1. GE 211 Programming in C++ Array &Matrix Dr. Ahmed Telba

2. Initializing an Array DataType ArrayName[dimension] = { element1, element2, …, elementn} ; examples of declaring an initializing arrays: int number[] = {18, 42, 25, 12, 34, 15, 63, 72, 92, 26, 26, 12}; double distance[] = {44.14, 720.52, 96.08, 468.78, 6.28};

3. #include using namespace std; int main() { double distance[] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "2nd member = " << distance[1] << endl; cout << "5th member = " << distance[4] << endl; return 0; } This would produce: 2nd member = 720.52 5th member = 6.28

4. #include using namespace std; int main() { double distance[] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "Distance 1: " << distance[0] << endl; cout << "Distance 2: " << distance[1] << endl; cout << "Distance 3: " << distance[2] << endl; cout << "Distance 4: " << distance[3] << endl; cout << "Distance 5: " << distance[4] << endl; return 0; } This would produce: Distance 1: 44.14 Distance 2: 720.52 Distance 3: 96.08 Distance 4: 468.78 Distance 5: 6.28

5. // You can use such a constant in a for loop to scan the array and access each of its members. Here is an example: #include using namespace std; int main() { const int numberOfItems = 5; double distance[numberOfItems] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "Members of the array\n"; for(int i = 0; i < numberOfItems; ++i) cout << "Distance " << i + 1 << ": " << distance[i] << endl; return 0; } In both cases, this would produce: Members of the array Distance 1: 44.14 Distance 2: 720.52 Distance 3: 96.08 Distance 4: 468.78 Distance 5: 6.28

6. Filling Up an Array When you declare an array without initializing it, we have mentioned that the compiler reserves an amount of memory space for the members of the array. But that is only what the compiler does. Each part of such reserved space is filled with garbage. Therefore, you must make sure that you know the value held by a member of the array before making any attempt to process the value held by that member of the array. Consider the following example: #include using namespace std; int main() { const int numberOfItems = 5; double distance[numberOfItems]; cout << "Distance 1: " << distance[0] << endl; cout << "Distance 2: " << distance[1] << endl; cout << "Distance 3: " << distance[2] << endl; cout << "Distance 4: " << distance[3] << endl; cout << "Distance 5: " << distance[4] << endl; return 0; } This would produce: Distance 1: -9.25596e+061 Distance 2: -9.25596e+061 Distance 3: -9.25596e+061 Distance 4: -9.25596e+061 Distance 5: -9.25596e+061

7. #include using namespace std; int main() { const int numberOfItems = 5; double distance[numberOfItems] = {44.14, 720.52, 96.08}; cout << "Distance 1: " << distance[0] << endl; cout << "Distance 2: " << distance[1] << endl; cout << "Distance 3: " << distance[2] << endl; cout << "Distance 4: " << distance[3] << endl; cout << "Distance 5: " << distance[4] << endl; return 0; } This would produce: Distance 1: 44.14 Distance 2: 720.52 Distance 3: 96.08 Distance 4: 0 Distance 5: 0

8. #include using namespace std; int main() { const int NumberOfItems = 5; double distance[NumberOfItems] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "Distance 1: " << distance[0] << endl; cout << "Distance 2: " << distance[1] << endl; cout << "Distance 3: " << distance[2] << endl; cout << "Distance 4: " << distance[3] << endl; cout << "Distance 5: " << distance[4] << endl; cout << "Distance 6: " << distance[5] << endl; cout << "Distance 7: " << distance[6] << endl; cout << "Distance 8: " << distance[7] << endl; return 0; } This would produce: Distance 1: 44.14 Distance 2: 720.52 Distance 3: 96.08 Distance 4: 468.78 Distance 5: 6.28 Distance 6: 2.64214e-308 Distance 7: 2.12414e-314 Distance 8: 1.00532e-307

9. Operations on Arrays #include using namespace std; int main() { // We know that we need a constant number of elements const int max = 10; int number[max]; // We will calculate their sum int sum = 0; cout << "Please type 10 integers.\n"; for( int i = 0; i < max; i++ ) { cout << "Number " << i + 1 << ": "; cin >> number[i]; sum += number[i]; } cout << "\n\nThe sum of these numbers is " << Sum << "\n\n"; return 0; } This would produce:Please type 10 integers. Number 1: 120 Number 2: 42 Number 3: 75 Number 4: 38 Number 5: 904 Number 6: 6 Number 7: 26 Number 8: 55 Number 9: 92 Number 10: 20 The sum of these numbers is 1378

10. // A 2-Dimensional array double distance[][4] = { { 44.14, 720.52, 96.08, 468.78 }, { 6.28, 68.04, 364.55, 6234.12 } }; using namespace std; int main() { // A 2-Dimensional array double distance[2][4] = {44.14, 720.52, 96.08, 468.78, 6.28, 68.04, 364.55, 6234.12}; // Scan the array from the 3rd to the 7th member cout << "Members of the array"; cout << "\nDistance [0][0]" << ": " << distance[0][0]; cout << "\nDistance [0][1]" << ": " << distance[0][1]; cout << "\nDistance [0][2]" << ": " << distance[0][2]; cout << "\nDistance [0][3]" << ": " << distance[0][3]; cout << "\nDistance [1][0]" << ": " << distance[1][0]; cout << "\nDistance [1][1]" << ": " << distance[1][1]; cout << "\nDistance [1][2]" << ": " << distance[1][2]; cout << "\nDistance [1][3]" << ": " << distance[1][3]; cout << endl; return 0; } This would produce: Members of the array Distance [0][0]: 44.14 Distance [0][1]: 720.52 Distance [0][2]: 96.08 Distance [0][3]: 468.78 Distance [1][0]: 6.28 Distance [1][1]: 68.04 Distance [1][2]: 364.55 Distance [1][3]: 6234.12

11. Multidimensional Arrays [0][0] [0][1] [0][2] [0][3] [0][4] [1][0] [1][1] [1][2] [1][3] [1][4] [2][0] [2][1] [2][2] [2][3] [2][4]  int anArray[3][5] ={ { 1, 2, 3, 4, 5, }, // row 0 { 6, 7, 8, 9, 10, }, // row 1 { 11, 12, 13, 14, 15 } // row 2 };

12. Matrix addition code #include void mult_matrices(int a[][3], int b[][3], int result[][3]); void print_matrix(int a[][3]); void main(void) { int p[3][3] = { {1, 3, -4}, {1, 1, -2}, {-1, -2, 5} }; int q[3][3] = { {8, 3, 0}, {3, 10, 2}, {0, 2, 6} }; int r[3][3]; mult_matrices(p, q, r); cout<<_matrix(r); }

13. void mult_matrices(int a[][3], int b[][3], int result[][3]) { int i, j, k; for(i=0; i<3; i++) { for(j=0; j<3; j++) { for(k=0; k<3; k++) { result[i][j] = a[i][k] + b[k][j]; } void print_matrix(int a[][3]) { int i, j; for (i=0; i<3; i++) { for (j=0; j<3; j++) { printf("%d\t", a[i][j]); } printf("\n"); }}

14. #include void add_matrices(int a[][3], int b[][3], int result[][3]); void print_matrix(int a[][3]); void main(void) { int p[3][3] = { {1, 3, -4}, {1, 1, -2}, {-1, -2, 5} }; int q[3][3] = { {8, 3, 0}, {3, 10, 2}, {0, 2, 6} }; int r[3][3]; add_matrices(p, q, r); printf("\nMatrix 1:\n"); print_matrix(p); printf("\nMatrix 2:\n"); print_matrix(q); printf("\nResult:\n"); print_matrix(r); } void add_matrices(int a[][3], int b[][3], int result[][3]) { int i, j; for(i=0; i<3; i++) { for(j=0; j<3; j++) { result[i][j] = a[i][j] + b[i][j]; } void print_matrix(int a[][3]) { int i, j; for (i=0; i<3; i++) { for (j=0; j<3; j++) { printf("%d\t", a[i][j]); } printf("\n"); }

15. Matrix addition

16. initialization of Two-Dimensional Array An two-dimensional array can be initialized along with declaration. For two-dimensional array initialization, elements of each row are enclosed within curly braces and separated by commas. All rows are enclosed within curly braces.

17. Referring to Array Elements To access the elements of a two-dimensional array, we need a pair of indices: one for the row position and one for the column position. The format is as simple as: name[rowIndex][columnIndex]

18. Arrays example #include using namespace std; int billy [] = {16, 2, 77, 40, 12071}; int n, result=0; int main () { for ( n=0 ; n<5 ; n++ ) { result += billy[n]; } cout << result; system("pause"); return 0; }

19. Multidimensional arrays Multidimensional arrays can be described as "arrays of arrays". For example, a bidimensional array can be imagined as a bidimensional table made of elements, all of them of a same uniform data type. int jimmy [3][5];

20. #define WIDTH 5 #define HEIGHT 3 int jimmy [HEIGHT][WIDTH]; int n,m; int main () { for (n=0;n<HEIGHT;n++) for (m=0;m<WIDTH;m++) { jimmy[n][m]=(n+1)*(m+1); } return 0; } jimmy[1][3]

21. #define HEIGHT 3 #define HEIGHT 4

22. // arrays as parameters #include using namespace std; void printarray (int arg[], int length) { for (int n=0; n<length; n++) cout << arg[n] << " "; cout << "\n"; } int main () { int firstarray[] = {5, 10, 15}; int secondarray[] = {2, 4, 6, 8, 10}; printarray (firstarray,3); printarray (secondarray,5); return 0; } 5 10 15 2 4 6 8 10

23. char myword[] = { 'H', 'e', 'l', 'l', 'o', '\0' }; / null-terminated sequences of characters #include using namespace std; int main () { char question[] = "Please, enter your first name: "; char greeting[] = "Hello, "; char yourname [80]; cout << question; cin >> yourname; cout << greeting << yourname << "!"; return 0; }

24. declaring an initializing arrays: Here are examples of declaring an initializing arrays: int number[12] = {18, 42, 25, 12, 34, 15, 63, 72, 92, 26, 26, 12}; double distance[5] = {44.14, 720.52, 96.08, 468.78, 6.28}; int number[] = {18, 42, 25, 12, 34, 15, 63, 72, 92, 26, 26, 12}; double distance[] = {44.14, 720.52, 96.08, 468.78, 6.28};

25. int n, m; double x[5][6]; FILE *inp; inp = fopen("IN.DAT","r"); for (n = 0; n < 5; ++n) { for (m = 0; m < 6; ++m) fscanf (inp, "%lf", &x[n][m]); } fclose (inp);

27. //adding Matrix #include void main() { clrscr(); int a[10][10],b[10][10],c[10][10],m,n,i,j; cout<<"Enter number of rows: "; cin>>m; cout<<"Enter number of coloumns: "; cin>>n; cout<<endl<<"Enter elements of matrix A: "<<endl; for(i=0;i<m;i++) { for(j=0;j<n;j++) { cout<<"Enter element a"<<i+1<<j+1<<": "; cin>>a[i][j]; } cout<<endl<<"Enter elements of matrix B: "<<endl; //Coding by: Snehil Khanor //http://WapCPP.blogspot.com for(i=0;i<m;i++) { for(j=0;j<n;j++) { cout<<"Enter element b"<<i+1<<j+1<<": "; cin>>b[i][j]; }

28. Diagonal Matrix 1 0 0 0 0 2 0 0 0 0 3 0 0 0 0 4 x(i,j) is on diagonal iff i = j number of diagonal elements in an n x n matrix is n non diagonal elements are zero store diagonal only vs n 2 whole

29. 29 Program 7-2 // This program asks the user for the number of hours worked // by 6 employees. It uses a 6-element short array to store the // values. #include void main(void) { short hours[6]; cout << "Enter the hours worked by six employees: "; for (int count = 0; count < 6; count++) cin >> hours[count]; cout << "The hours you entered are:"; for (count = 0; count < 6; count++) cout << " " << hours[count]; cout << endl; }

30. 30 Program 7-6 // This program displays the number of days in each month. // It uses a 12-element int array. #include void main(void) { int days[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; for (int count = 0; count < 12; count++) { cout << "Month " << (count + 1) << " has "; cout << days[count] << " days.\n"; }

31. 31 Program Output Month 1 has 31 days. Month 2 has 28 days. Month 3 has 31 days. Month 4 has 30 days. Month 5 has 31 days. Month 6 has 30 days. Month 7 has 31 days. Month 8 has 31 days. Month 9 has 30 days. Month 10 has 31 days. Month 11 has 30 days. Month 12 has 31 days.

32. #include using namespace std; void MultiplyWithOutAMP() { int aMatrix[3][2] = {{1, 4}, {2, 5}, {3, 6}}; int bMatrix[2][3] = {{7, 8, 9}, {10, 11, 12}}; int product[3][3] = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}}; for (int row = 0; row < 3; row++) { for (int col = 0; col < 3; col++) { // Multiply the row of A by the column of B to get the row, column of product. for (int inner = 0; inner < 2; inner++) { product[row][col] += aMatrix[row][inner] * bMatrix[inner][col]; } cout << product[row][col] << " "; } cout << "\n"; } int main() { // cout << bMatrix[3][2] << "\t"; // cout << aMatrix[3][2] << "\t"; MultiplyWithOutAMP(); getchar(); system("pause"); return 0; }

33. Using pointer(Multiplier) #include using namespace std; int main() { int **mat1; int **mat2; int **result; int row,col; cout<<"Please enter row/col"<<endl; cin>>row>>col; mat1 = new int *[row]; mat2 = new int *[row]; result = new int *[row]; int k,i,j; for (k=0; i<row; k++) mat1[k] = new int[col]; mat2[k] = new int[col]; result[k] = new int[col]; for (i=0; i<row; i++) for (j=0; j<col; j++) for (j=0; j<row; j++) for(i=0; i<col; i++) result[i][k] += (mat1 [i][k] * mat2[k][j]); cout<<setw(4)<<result[i][k];

34. #include // pointer Multiplier #include using namespace std; int main() { int **mat1; int **mat2; int **result; int row,col; cout<<"Please enter row/col"<<endl; cin>>row>>col; mat1 = new int *[row]; mat2 = new int *[row]; result = new int *[row]; int k,i,j; for (k=0; k<row; k++) mat1[k] = new int[col]; mat2[k] = new int[col]; result[k] = new int[col]; for (i=0; i<row; i++) for (j=0; j<col; j++) mat1[k][i] = k + i; for (j=0; j<row; j++) mat2[i][k] = j + k; for(i=0; i<col; i++) result[i][k] += (mat1 [i][k] * mat2[k][j]); cout<<setw(4)<<result[i][k];

35. cout<<endl<<"Displaying Matrix A: "<<endl<<endl; for(i=0;i<m;i++) { for(j=0;j<n;j++) { cout<<a[i][j]<<" "; } cout<<endl<<endl; } cout<<endl<<"Displaying Matrix B: "<<endl<<endl; for(i=0;i<m;i++) { for(j=0;j<n;j++) { cout<<b[i][j]<<" "; } cout<<endl<<endl; } cout<<endl<<"Matrix A + Matrix B = Matrix C: "<<endl<<endl; for(i=0;i<m;i++) { for(j=0;j<n;j++) { cout<<a[i][j]+b[i][j]<<" "; } cout<<endl<<endl; } getch(); }

36. Adding matrix: c++ program to add two matrices #include using namespace std; main() { int m, n, c, d, first[10][10], second[10][10], sum[10][10]; cout << "Enter the number of rows and columns of matrix "; cin >> m >> n; cout << "Enter the elements of first matrix\n"; for ( c = 0 ; c < m ; c++ ) for ( d = 0 ; d < n ; d++ ) cin >> first[c][d]; cout << "Enter the elements of second matrix\n"; for ( c = 0 ; c < m ;c++ ) for ( d = 0 ; d < n ; d++ ) cin >> second[c][d]; for ( c = 0 ; c < m ; c++ ) for ( d = 0 ; d < n ; d++ ) sum[c][d] = first[c][d] + second[c][d]; cout << "Sum of entered matrices:-\n"; for ( c = 0 ; c < m ; c++ ) { for ( d = 0 ; d < n ; d++ ) cout << sum[c][d] << "\t"; cout << endl; } system("pause"); return 0; }

37. A number is taken from the user number with reverse digits is displayed #include using namespace std; int main() { //clrscr(); long int n,rev=0,m; cout<<"please enter a five digit no.: "; cin>>n; while(n>0) //Coding by: Snehil Khanor //http://WapCPP.blogspot.com { m=n%10; rev=rev*10+m; n=n/10; } cout<<rev; // system("pause"); return 0; }

38. Address in memory 1: #include 2: 3: int main() 4: { 5: short age[4]; 6: age[0]=23; 7: age[1]=34; 8: age[2]=65; 9: age[3]=74; 10: 11: std::cout << age << std::endl; 12: return 0; 13: }

39. Character in Array 1: char letter[4]; 2: letter[0]='M'; 3: letter[1]='a'; 4: letter[2]='r'; 5: letter[3]='k'; 6:... *(letter+2)...

44. Question (4) Using the switch or if statement, write a C program that takes in an integer numerical grade num_grade from the keyboard and returns to the screen a letter_grade according to the following scale: letter_grade is A if num_grade ≥ 90 letter_grade is B if 80 ≤ num_grade < 90 letter_grade is C if 70 ≤ num_grade < 80 letter_grade is D if 60 ≤ num_grade < 70 letter_grade is F if num_grade < 60 Check the correctness of your program and print down the outputs of your program for a student with a score of 100 and another with a score of 65.

46. include using namespace std; int main() { double distance[] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "2nd member = " << distance[1] << endl; cout << "5th member = " << distance[4] << endl; return 0; } This would produce: 2nd member = 720.52 5th member = 6.28

47. #include using namespace std; int main() { double distance[] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "Distance 1: " << distance[0] << endl; cout << "Distance 2: " << distance[1] << endl; cout << "Distance 3: " << distance[2] << endl; cout << "Distance 4: " << distance[3] << endl; cout << "Distance 5: " << distance[4] << endl; return 0; } This would produce: Distance 1: 44.14 Distance 2: 720.52 Distance 3: 96.08 Distance 4: 468.78 Distance 5: 6.28

48. #include using namespace std; int main() { const int numberOfItems = 5; double distance[numberOfItems] = {44.14, 720.52, 96.08, 468.78, 6.28}; cout << "Distance 1: " << distance[0] << endl; cout << "Distance 2: " << distance[1] << endl; cout << "Distance 3: " << distance[2] << endl; cout << "Distance 4: " << distance[3] << endl; cout << "Distance 5: " << distance[4] << endl; return 0; }

49. #include using namespace std; int main() { // We know that we need a constant number of elements const int max = 10; int number[max]; // We will calculate their sum int sum = 0; cout << "Please type 10 integers.\n"; for( int i = 0; i < max; i++ ) { cout << "Number " << i + 1 << ": "; cin >> number[i]; sum += number[i]; } cout << "\n\nThe sum of these numbers is " << Sum << "\n\n"; return 0; }

50. #include using namespace std; void DisplayTheArray(double member[5]); int main() { const int numberOfItems = 5; double distance[numberOfItems] = {44.14, 720.52, 96.08, 468.78, 6.28}; return 0; } void DisplayTheArray(double member[5]) { for(int i = 0; i < 5; ++i) cout << "\nDistance " << i + 1 << ": " << member[i]; cout << endl; }

51. Declaring and Initializing a 2-Dimensional Array #include using namespace std; int main() { // A 2-Dimensional array double distance[2][4] = {44.14, 720.52, 96.08, 468.78, 6.28, 68.04, 364.55, 6234.12}; // Scan the array from the 3rd to the 7th member cout << "Members of the array"; cout << "\nDistance [0][0]" << ": " << distance[0][0]; cout << "\nDistance [0][1]" << ": " << distance[0][1]; cout << "\nDistance [0][2]" << ": " << distance[0][2]; cout << "\nDistance [0][3]" << ": " << distance[0][3]; cout << "\nDistance [1][0]" << ": " << distance[1][0]; cout << "\nDistance [1][1]" << ": " << distance[1][1]; cout << "\nDistance [1][2]" << ": " << distance[1][2]; cout << "\nDistance [1][3]" << ": " << distance[1][3]; cout << endl; return 0; }

52. 2-Dimensional array #include using namespace std; int main() { // A 2-Dimensional array double distance[][4] = { { 44.14, 720.52, 96.08, 468.78 }, { 6.28, 68.04, 364.55, 6234.12 } }; // Scan the array from the 3rd to the 7th member cout << "Members of the array"; for(int i = 0; i < 2; ++i) for(int j = 0; j < 4; ++j) cout << "\nDistance [" << i << "][" << j << "]: " << distance[i][j]; cout << endl; return 0; }

53. Multidimensional Arrays

54. #include using namespace std; void MultiplyWithOutAMP() { int aMatrix[3][2] = {{1, 4}, {2, 5}, {3, 6}}; int bMatrix[2][3] = {{7, 8, 9}, {10, 11, 12}}; int product[3][3] = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}}; for (int row = 0; row < 3; row++) { for (int col = 0; col < 3; col++) { // Multiply the row of A by the column of B to get the row, column of product. for (int inner = 0; inner < 2; inner++) { product[row][col] += aMatrix[row][inner] * bMatrix[inner][col]; } std::cout << product[row][col] << " "; } std::cout << "\n"; } main() { MultiplyWithOutAMP(); getchar(); system("pause"); }

55. #include using namespace std; #define MAX 50 void mulmatvec(int m, int n, double a[MAX][MAX], double x[MAX], double b[MAX]){ int i,j; for(i = 0; i < m; i++){ b[i] = 0.; for(j = 0; j < n; j++) b[i] += a[i][j]*x[j]; } return; } int main(){ int i,j,m,n; double a[MAX][MAX], x[MAX], b[MAX]; cout << "Enter the number of rows in the matrix \n"; cin >> m; cout << "Enter the number of columns in the matrix \n"; cin >> n; cout << "Enter the matrix by rows\n"; for(i = 0; i < m; i++) for(j = 0; j < n; j++) cin >> a[i][j]; cout << "Enter the vector\n"; for(j = 0; j < n; j++) cin >> x[j]; mulmatvec(m,n,a,x,b); cout << "\nA*x = \n"; for(i = 0; i < m; i++) cout << b[i] << "\n"; }

58. #include using namespace std; int main(){ int i,j; int arr[6][6]; for(i=0;i<=5;i++){ for(j=5;j>=0;j--){ if(i+j==5) arr[i][j]=0; 'diagonal else if(i+j>5) arr[i][j]=-1; 'lower-right side else arr[i][j]=1; 'upper-left side } } for(i=0;i<=5;i++){ for(j=0;j<=5;j++) cout<<arr[i][j]<<"\t"; cout<<endl; } getch(); return 0; }

59. Initializing array To assign values to the array, you can write those values as below. int i[]= {1, 2, 3, 4, 5};//The array got values or int i[5]; i[0]=1; i[1]=2; i[2]=3; i[3]=4; i[4]=5;

60. Adding two Matrix #include using namespace std; main() { int m, n, c, d, first[10][10], second[10][10], sum[10][10]; cout << "Enter the number of rows and columns of matrix "; cin >> m >> n; cout << "Enter the elements of first matrix\n"; for ( c = 0 ; c < m ; c++ ) for ( d = 0 ; d < n ; d++ ) cin >> first[c][d]; cout << "Enter the elements of second matrix\n"; for ( c = 0 ; c < m ;c++ ) for ( d = 0 ; d < n ; d++ ) cin >> second[c][d]; for ( c = 0 ; c < m ; c++ ) for ( d = 0 ; d < n ; d++ ) sum[c][d] = first[c][d] + second[c][d]; cout << "Sum of entered matrices:-\n"; for ( c = 0 ; c < m ; c++ ) { for ( d = 0 ; d < n ; d++ ) cout << sum[c][d] << "\t"; cout << endl; } return 0; }

61. Matrix multiplication in C++ Matrices can be used to perform transformations. For example, in 2D and 3D space. Transformations include, but are not limited to, rotating, scaling and translating. Transformations can be combined by multiplying the matrices with each other. Matricestransformationsrotatingscalingtranslating For example, you might want to: scale an object with a factor of 2 rotate it 45 degrees around the Y-axis translate it to (5,5,5) Each of the above steps can be represented with a four by four matrix (four rows and four columns). Multiplication of matrices is done by multiplying each row of the first matrix with each column of the second matrix and summing up the results. The number of columns of the first matrix needs to be equal to the number of rows of the second matrix. For example (4 x 4) x (4 x 4) is allowed. However, (4 x 3) x (4 x 3) is not allowed.

62. Matrix multiplication [[1x1 + 2x0 + 3x0 + 4x0] = 1, [1x0 + 2x1 + 3x0 + 4x0] = 2, [1x0 + 2x0 + 3x1 + 4x0] = 3, [1x0 + 2x0 + 3x0 + 4x1] = 4]]

65. Code #include void MultiplyWithOutAMP() { int aMatrix[3][2] = {{1, 4}, {2, 5}, {3, 6}}; int bMatrix[2][3] = {{7, 8, 9}, {10, 11, 12}}; int product[3][3] = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}}; for (int row = 0; row < 3; row++) { for (int col = 0; col < 3; col++) { // Multiply the row of A by the column of B to get the row, column of product. for (int inner = 0; inner < 2; inner++) { product[row][col] += aMatrix[row][inner] * bMatrix[inner][col]; } std::cout << product[row][col] << " "; } std::cout << "\n"; } void main() { MultiplyWithOutAMP(); getchar(); }

66. // C++ multiplication of the matrix x and matrix y and stores the result in matrix z #include using namespace std; #define m 3 #define c 2 #define n 4 int main(void) { int i, j, k; // first matrix int x[m][c] = {{1,2},{3,4},{5,6}}; // second matrix int y[c][n] = {{7,8,9,10},{11,12,13,14}}; // for storing the matrix product result int z[m][n]; for(i=0; i<m; i++) for(j=0; j<n; j++) { z[i][j] = 0; for(k=0; k<c; k++) // same as z[i][j] = z[i][j] + x[i][k] * y[k][j]; z[i][j] += x[i][k] * y[k][j]; } cout<<"\nMultiply matrix x and matrix y,"; cout<<"\nThen store the result in matrix z."; cout<<"\nMatrix x is 3x2, and matrix y is 2x4,"; cout<<"\nso, the result, z should be matrix 3x4\n"; cout<<"\nThe matrix product is: \n"; for (i=0; i<m; i++) { cout<<"\n"; for(j=0; j<n; j++) // display the result... cout<<" "<<z[i][j]; } cout<<endl; return 0; } Output example: Multiply matrix x and matrix y, Then store the result in matrix z. Matrix x is 3x2, and matrix y is 2x4, so, the result, z should be matrix 3x4 The matrix product is: 29 32 35 38 65 72 79 86 101 112 123 134 Press any key to continue...

67. 67 Chapter 7 – Arrays

68. 68 7.1 Arrays Hold Multiple values Unlike regular variables, arrays can hold multiple values.

69. 69 Figure 7-1 int count Enough memory for 1 int 12345 float price Enough memory for 1 float 56.981 char letter Enough memory for 1 char A

70. 70 Figure 7-2

71. 71 Table 7-1

72. 72 7.2 Accessing Array elements The individual elements of an array are assigned unique subscripts. These subscripts are used to access the elements.

73. 73 Program 7-1 // This program asks the user for the number of hours worked // by 6 employees. It uses a 6-element int array to store the // values. #include void main(void) { short hours[6]; cout << "Enter the hours worked by six employees: "; cin >> hours[0]; cin >> hours[1]; cin >> hours[2]; cin >> hours[3];

74. 74 Program continues cin >> hours[4]; cin >> hours[5]; cout << "The hours you entered are:"; cout << " " << hours[0]; cout << " " << hours[1]; cout << " " << hours[2]; cout << " " << hours[3]; cout << " " << hours[4]; cout << " " << hours[5] << endl; }

75. 75 Program Output with Example Input Enter the hours worked by six employees: 20 12 40 30 30 15 [Enter] The hours you entered are: 20 12 40 30 30 15

76. 76 Figure 7-7

77. 77 Program 7-2 // This program asks the user for the number of hours worked // by 6 employees. It uses a 6-element short array to store the // values. #include void main(void) { short hours[6]; cout << "Enter the hours worked by six employees: "; for (int count = 0; count < 6; count++) cin >> hours[count]; cout << "The hours you entered are:"; for (count = 0; count < 6; count++) cout << " " << hours[count]; cout << endl; }

78. 78 Program Output with Example Input Enter the hours worked by six employees: 20 12 40 30 30 15 [Enter] The hours you entered are: 20 12 40 30 30 15

79. 79 Program 7-3 // This program asks the user for the number of hours worked // by 6 employees. It uses a 6-element short array to store the // values. #include void main(void) { short hours[6]; cout << "Enter the hours worked by six employees.\n"; for (int count = 1; count <= 6; count++) { cout << "Employee " << count << ": "; cin >> hours[count - 1]; } cout << "The hours you entered are\n";

80. 80 Program continues for (count = 1; count <= 6; count++) { cout << "Employee " << count << ": "; cout << hours[count - 1] << endl; }

81. 81 Program Output with Example Input Enter the hours worked by six employees. Employee 1: 20 [Enter] Employee 2: 12 [Enter] Employee 3: 40 [Enter] Employee 4: 30 [Enter] Employee 5: 30 [Enter] Employee 6: 15 [Enter] The hours you entered are Employee 1: 20 Employee 2: 12 Employee 3: 40 Employee 4: 30 Employee 5: 30 Employee 6: 15

82. 82 7.3 No Bounds Checking in C++ C++ gives you the freedom to store data past an array’s boundaries.

83. 83 Program 7-4 // This program unsafely accesses an area of memory by writing // values beyond an array's boundary. // WARNING: If you compile and run this program, it could cause // the computer to crash. #include void main(void) { short values[3]; // An array of 3 short integers. cout << "I will store 5 numbers in a 3 element array!\n"; for (int count = 0; count < 5; count++) values[count] = 100; cout << "If you see this message, it means the computer\n"; cout << "has not crashed! Here are the numbers:\n"; for (int count = 0; count < 5; count++) cout << values[count] << endl; }

84. 84 Figure 7-8

85. 85 7.4 Array Initialization Arrays may be initialized when they are declared.

86. 86 Program 7-5 // This program displays the number of days in each month. // It uses a 12-element int array. #include void main(void) { int days[12]; days[0] = 31; // January days[1] = 28; // February days[2] = 31; // March days[3] = 30; // April days[4] = 31; // May days[5] = 30; // June days[6] = 31; // July

87. 87 Program continues days[7] = 31; // August days[8] = 30; // September days[9] = 31; // October days[10] = 30; // November days[11] = 31; // December for (int count = 0; count < 12; count++) { cout << "Month " << (count + 1) << " has "; cout << days[count] << " days.\n"; }

88. 88 Program Output Month 1 has 31 days. Month 2 has 28 days. Month 3 has 31 days. Month 4 has 30 days. Month 5 has 31 days. Month 6 has 30 days. Month 7 has 31 days. Month 8 has 31 days. Month 9 has 30 days. Month 10 has 31 days. Month 11 has 30 days. Month 12 has 31 days.

89. 89 Program 7-6 // This program displays the number of days in each month. // It uses a 12-element int array. #include void main(void) { int days[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; for (int count = 0; count < 12; count++) { cout << "Month " << (count + 1) << " has "; cout << days[count] << " days.\n"; }

90. 90 Program Output Month 1 has 31 days. Month 2 has 28 days. Month 3 has 31 days. Month 4 has 30 days. Month 5 has 31 days. Month 6 has 30 days. Month 7 has 31 days. Month 8 has 31 days. Month 9 has 30 days. Month 10 has 31 days. Month 11 has 30 days. Month 12 has 31 days.

91. 91 Program 7-7 // This program uses an array of ten characters to store the // first ten letters of the alphabet. The ASCII codes of the // characters are displayed. #include void main(void) { char letters[10] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J'}; cout << "Character" << "\t" << "ASCII Code\n"; cout << "--------" << "\t" << "----------\n"; for (int count = 0; count < 10; count++) { cout << letters[count] << "\t\t"; cout << int(letters[count]) << endl; }

92. 92 Program Output CharacterASCII Code --------- ---------- A65 B66 C67 D68 E69 F70 G71 H72 I73 J74

93. 93 Partial Array Initialization When an array is being initialized, C++ does not require a value for every element. int numbers[7] = {1, 2, 4, 8};

94. 94 Program 7-8 // This program has a partially initialized array. #include void main(void) { int numbers[7] = {1, 2, 4, 8}; // Initialize the // first 4 elements. cout << "Here are the contents of the array:\n"; for (int index = 0; index < 7; index++) cout << numbers[index] << endl; }

95. 95 Program Output Here are the contents of the array: 1 2 4 8 0

96. 96 Implicit Array Sizing It is possible to declare an array without specifying its size, as long as you provide an initialization list. float ratings[] = {1.0, 1.5, 2.0, 2.5, 3.0};

97. 97 Initializing With Strings When initializing a character array with a string, simply enclose the string in quotation marks: char name[] = “Warren”;

98. 98 Figure 7-11

99. 99 Program 7-9 // This program displays the contents of two char arrays. #include void main(void) { char name1[] = "Holly"; char name2[] = {'W', 'a', 'r', 'r', 'e', 'n', '\0'}; cout << name1 << endl; cout << name2 << endl; }

100. 100 Program Output Holly Warren

101. 101 7.5 Processing Array Contents Individual array elements are processed like any other type of variable.

102. 102 Program 7-10 // This program stores, in an array, the hours worked by 5 // employees who all make the same hourly wage. #include void main(void) { int hours[5]; float payRate; cout << "Enter the hours worked by 5 employees who all\n"; cout << "earn the same hourly rate.\n"; for (int index = 0; index < 5; index++) { cout << "Employee #" << (index + 1) << ": "; cin >> hours[index]; }

103. 103 Program continues cout << "Enter the hourly pay rate for all the employees: "; cin >> payRate; cout << "Here is the gross pay for each employee:\n"; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); for (index = 0; index < 5; index++) { float grossPay = hours[index] * payRate; cout << "Employee #" << (index + 1); cout << ": $" << grossPay << endl; }

104. 104 Program Output with Example Input Enter the hours worked by 5 employees who all earn the same hourly rate. Employee #1: 5 [Enter] Employee #2: 10 [Enter] Employee #3: 15 [Enter] Employee #4: 20 [Enter] Employee #5: 40 [Enter] Enter the hourly pay rate for all the employees: 12.75 [Enter] Here is the gross pay for each employee: Employee #1: $63.75 Employee #2: $127.50 Employee #3: $191.25 Employee #4: $255.00 Employee #5: $510.00

105. 105 Program 7-11 // This program stores, in an array, the hours worked by 5 // employees who all make the same hourly wage. It then // displays the gross pay, including any overtime. #include // Constant for defining the array size void main(void) { int hours[5]; float payRate; cout << "Enter the hours worked by 5 employees who all\n"; cout << "earn the same hourly rate.\n"; for (int index = 0; index < 5; index++) { cout << "Employee #" << (index + 1) << ": "; cin >> hours[index]; }

106. 106 Program continues cout << "Enter the hourly pay rate for all the employees: "; cin >> payRate; cout << "Here is the gross pay for each employee:\n"; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); for (index = 0; index < 5; index++) { float grossPay, overTime; if (hours[index] > 40) { // Calculate pay for 40 hours. grossPay = 40 * payRate; // Calculate overtime pay. overTime = (hours[index] - 40) * 1.5 * payRate; // Add regular pay and overtime pay. grossPay += overTime; }

107. 107 Program continues else grossPay = hours[index] * payRate; cout << "Employee #" << (index + 1); cout << ": $" << grossPay << endl; }

108. 108 Program Output with Example Input Enter the hours worked by 5 employees who all earn the same hourly rate. Employee #1: 10 [Enter] Employee #2: 20 [Enter] Employee #3: 50 [Enter] Employee #4: 40 [Enter] Employee #5: 60 [Enter] Enter the hourly pay rate for all the employees: 12.75 [Enter] Here is the gross pay for each employee: Employee #1: $127.50 Employee #2: $255.00 Employee #3: $701.25 Employee #4: $510.00 Employee #5: $892.50

109. 109 7.6 Focus on Software Engineering: Parallel Arrays By using he same subscript, you can build relationships between data stored in two or more arrays.

110. 110 Program 7-12 // This program stores, in two arrays, the hours worked by 5 // employees, and their hourly pay rates. #include // Constant for defining the array size const int numEmps = 5; void main(void) { int hours[numEmps]; float payRate[numEmps]; cout << "Enter the hours worked by “ << numEmps << “ employees and their\n"; cout << "hourly rates.\n"; for (int index = 0; index < numEmps; index++) { cout << "hours worked by employee #" << (index + 1); cout << ": ";

111. 111 Program continues cin >> hours[index]; cout << "Hourly pay rate for employee #"; cout << (index + 1) << ": "; cin >> payRate[index]; } cout << "Here is the gross pay for each employee:\n"; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); for (index = 0; index < numEmps; index++) { float grossPay = hours[index] * payRate[index]; cout << "Employee #" << (index + 1); cout << ": $" << grossPay << endl; }

112. 112 Program Output with Example Input Enter the hours worked by 5 employees and their hourly rates. hours worked by employee #1: 10 [Enter] Hourly pay rate for employee #1: 9.75 [Enter] hours worked by employee #2: 15 [Enter] Hourly pay rate for employee #2: 8.62 [Enter] hours worked by employee #3: 20 [Enter] Hourly pay rate for employee #3: 10.50 [Enter] hours worked by employee #4: 40 [Enter] Hourly pay rate for employee #4: 18.75 [Enter] hours worked by employee #5: 40 [Enter] Hourly pay rate for employee #5: 15.65 [Enter] Here is the gross pay for each employee: Employee #1: $97.50 Employee #2: $129.30 Employee #3: $210.00

113. 113 7.7 Thou Shalt Not Assign You cannot use the assignment operator to copy one array’s contents to another. for (int count=0; count < 4; count++) newVal[count] = oldVal[count];

114. 114 Table 7-2

115. 115 7.8 Printing the Contents of an Array To display the contents of an array, you must use a loop to display the contents of each element. int array[5] = { 10, 20, 30, 40, 50 }; for (int count = 0; count < 5; count++) cout << array[count] << endl;

116. 116 7.9 Arrays As Function Arguments To pass an array as an argument to a function, pass the name of the array.

117. 117 Program 7-13 // This program demonstrates that an array element is passed // to a function like any other variable. #include void ShowValue(int);// Function prototype void main(void) { int collection[8] = {5, 10, 15, 20, 25, 30, 35, 40}; for (int Cycle = 0; Cycle < 8; Cycle++) ShowValue(collection[Cycle]); }

118. 118 Program continues //************************************ // Definition of function showValue. * // This function accepts an integer argument. * // The value of the argument is displayed. * //************************************ void ShowValue(int Num) { cout << Num << " "; }

119. 119 Program Output 5 10 15 20 25 30 35 40

120. 120 Program 7-14 // This program demonstrates an array being passed to a function. #include void showValues(int []);// Function prototype void main(void) { int collection[8] = {5, 10, 15, 20, 25, 30, 35, 40}; showValues(collection); // Passing address of array collection } //*********************************************** // Definition of function showValues. * // This function accepts an array of 8 integers * // as its argument. The contents of the array * // is displayed. * //*********************************************** void showValues(int nums[]) { for (int index = 0; index < 8; index++) cout << nums[index] << " "; }

121. 121 Program Output 5 10 15 20 25 30 35 40

122. 122 Program 7-15 // This program demonstrates an array being passed to a function. #include void showValues(int []);// Function prototype void main(void) { int set1[8] = {5, 10, 15, 20, 25, 30, 35, 40}; int set2[8] = {2, 4, 6, 8, 10, 12, 14, 16}; showValues(set1); cout << endl; showValues(set2); } //*********************************************** // Definition of function showValues. * // This function accepts an array of 8 integers * // as its argument. The contents of the array * // is displayed. * //*********************************************** void showValues(int nums[]) { for (int index = 0; index < 8; index++) cout << nums[index] << " "; }

123. 123 Program Output 5 10 15 20 25 30 35 40 2 4 6 8 10 12 14 16

124. 124 Program 7-16 // This program uses a function that can display the contents // of an integer array of any size. #include void showValues(int [], int);// Function prototype void main(void) { int set1[8] = {5, 10, 15, 20, 25, 30, 35, 40}; int set2[4] = {2, 4, 6, 8}; int set3[12] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}; showValues(set1, 8); cout << endl; showValues(set2, 4); cout << endl; showValues(set3, 12); }

125. 125 Program continues //*********************************************** // Definition of function showValues. * // This function displays the contents of the * // array passed into nums. The value passed * // into elements is the number of elements in * // the nums array. * //*********************************************** void showValues(int nums[], int elements) { for (int index = 0; index < elements; index++) cout << nums[index] << " "; }

126. 126 Program Output 5 10 15 20 25 30 35 40 2 4 6 8 1 2 3 4 5 6 7 8 9 10 11 12

127. 127 Program 7-17 // This program uses a function that doubles the contents of // the elements within an array. #include void doubleArray(int [], int);// Function prototype const int arraySize = 12; void main(void) { int set[arraySize] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}; cout << "The arrays values are:\n"; for (int index = 0; index < arraySize; index++) cout << set[index] << " "; cout << endl; doubleArray(set, arraySize); cout << "After calling doubleArray, the values are:\n";

128. 128 Program continues for (int index = 0; index < arraySize; index++) cout << set[index] << " "; cout << endl; } //************************************************** // Definition of function doubleArray. * // This function doubles the value of each element * // in the array passed into nums. * // The value passed into size is the number of * // elements in the nums array. * //************************************************** void doubleArray(int nums[], int size) { for (int index = 0; index < size; index++) nums[index] *= 2; }

129. 129 Program Output The array values are: 1 2 3 4 5 6 7 8 9 10 11 12 After calling doubleArray, the values are: 2 4 6 8 10 12 14 16 18 20 22 24

130. 130 7.10 Two-dimensional Arrays A two-dimensional array is like several identical arrays put together. It is useful for storing multiple sets of data.

131. 131 Program 7-18 // This program demonstrates a two-dimensional array. #include void main(void) { float sales[3][4]; // 2D array, 3 rows and 4 columns. float totalSales = 0;// To hold the total sales. int dir, qtr;// Loop counters.

132. 132 Program continues cout << "This program will calculate the total sales of\n"; cout << "all the company's divisions.\n"; cout << "Enter the following sales information:\n\n"; // Nested loops to fill the array with quarterly // sales figures for each division. for (div = 0; div < 3; div++) { for (qtr = 0; qtr < 4; qtr++) { cout << "Division " << (div + 1); cout << ", Quarter " << (qtr + 1) << ": $"; cin >> sales[div][qtr]; } cout << endl; // Print blank line. }

133. 133 Program continues // Nested loops to add all the elements. for (div = 0; div < 3; div++) for (qtr = 0; qtr < 4; qtr++) totalSales += sales[div][qtr]; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); cout << "The total sales for the company are: $"; cout << totalSales << endl; }

134. 134 Program Output with Example Input This program will calculate the total sales of all the company's divisions. Enter the following sales information: Division 1, Quarter 1: $31569.45 [Enter] Division 1, Quarter 2: $29654.23 [Enter] Division 1, Quarter 3: $32982.54 [Enter] Division 1, Quarter 4: $39651.21 [Enter] Division 2, Quarter 1: $56321.02 [Enter] Division 2, Quarter 2: $54128.63 [Enter] Division 2, Quarter 3: $41235.85 [Enter] Division 2, Quarter 4: $54652.33 [Enter]

135. 135 Output continues Division 3, Quarter 1: $29654.35 [Enter] Division 3, Quarter 2: $28963.32 [Enter] Division 3, Quarter 3: $25353.55 [Enter] Division 3, Quarter 4: $32615.88 [Enter] The total sales for the company are: $456782.34

136. 136 Passing Two-dimensional Arrays to Functions When a two-dimensional array is passed to a function, the parameter type must contain a size declarator for the number of columns.

137. 137 7.11 Arrays of Strings A two-dimensional array of characters can be used as an array of C-strings.

138. 138 Program 7-20 // This program displays the number of days in each month. // It uses a two-dimensional character array to hold the // names of the months and an int array to hold the number // of days. #include void main(void) { char months[12][10] = {"January", "February", "March", "April", "May", "June", "July", "August", "September”, "October", "November","December"}; int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; for (int count = 0; count < 12; count++) { cout << months[count] << " has "; cout << days[count] << " days.\n"; } }

139. 139 Program 7-20 (continued) Program Output January has 31 days. February has 28 days. March has 31 days. April has 30 days. May has 31 days. June has 30 days. July has 31 days. August has 31 days. September has 30 days. October has 31 days. November has 30 days. December has 31 days.

140. 140 Three Dimensional Arrays and Beyond C++ allows you to create arrays with virtually any number of dimensions. Here is an example of a three-dimensional array declaration: float seat[3][5][8];

141. 141 7.14 Introduction to the STL vector The Standard Template Library (or STL) is a collection of data types and algorithms that you may use in your programs. These data types and algorithms are programmer- defined. They are not part of the C++ language, but were created in addition to the built-in data types.

142. 142 7.14 Introduction to the STL vector The data types that are defined in the STL are commonly called containers, because they store and organize data. There are two types of containers in the STL: sequence containers and associative containers. The vector data type is a sequence container.

143. 143 7.14 Introduction to the STL vector A vector is like an array in the following ways: – A vector holds a sequence of values, or elements. – A vector stores its elements in contiguous memory locations. – You can use the array subscript operator [] to read the individual elements in the vector

144. 144 7.14 Introduction to the STL vector However, a vector offers several advantages over arrays. Here are just a few: – You do not have to declare the number of elements that the vector will have. – If you add a value to a vector that is already full, the vector will automatically increase its size to accommodate the new value. – vector s can report the number of elements they contain.

145. 145 Declaring a vector To use vectors in your program, you must first #include the vector header file with the following statement: #include Note: There is no.h at the end of the file name.

146. 146 Declaring a vector The next step is to include the following statement after your #include statements: using namespace std; The STL uses namespaces to organize the names of its data types and algorithms.

147. 147 Declaring a vector Now you are ready to declare an actual vector object. Here is an example: vector numbers; The statement above declares numbers as a vector of int s.

148. 148 Declaring a vector You can declare a starting size, if you prefer. Here is an example: vector numbers(10); The statement above declares numbers as a vector of 10 int s.

149. 149 Other examples of vector Declarations Declaration FormatDescription vector amounts; Declares amounts as an empty vector of float s. vector scores(15); Declares scores as a vector of 15 int s. vector letters(25, 'A'); Declares letters as a vector of 25 characters. Each element is initialized with 'A'. vector values2(values1); Declares values2 as a vector of double s. All the elements of values1, which also a vector of doubles, are copied to value2.

150. 150 Storing and Retrieving Values in a vector To store a value in an element that already exists in a vector, you may use the array subscript operator [].

151. 151 Program 7-23 // This program stores, in two vectors, the hours worked by 5 // employees, and their hourly pay rates. #include #include // Needed to declare vectors using namespace std; void main(void) { vector hours(5); // Declare a vector of 5 integers vector payRate(5); // Declare a vector of 5 floats cout > hours[index]; cout > payRate[index]; }

152. 152 Program 7-23 (continued) cout << "Here is the gross pay for each employee:\n"; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); for (index = 0; index < 5; index++) { float grossPay = hours[index] * payRate[index]; cout << "Employee #" << (index + 1); cout << ": $" << grossPay << endl; } }

153. 153 Program 7-23 (continued) Program Output with Example Input Shown in Bold Enter the hours worked by 5 employees and their hourly rates. Hours worked by employee #1: 10 [Enter] Hourly pay rate for employee #1: 9.75 [Enter] Hours worked by employee #2: 15 [Enter] Hourly pay rate for employee #2: 8.62 [Enter] Hours worked by employee #3: 20 [Enter] Hourly pay rate for employee #3: 10.50 [Enter] Hours worked by employee #4: 40 [Enter] Hourly pay rate for employee #4: 18.75 [Enter] Hours worked by employee #5: 40 [Enter] Hourly pay rate for employee #5: 15.65 [Enter] Here is the gross pay for each employee: Employee #1: $97.50 Employee #2: $129.30 Employee #3: $210.00 Employee #4: $750.00 Employee #5: $626.00

154. 154 Using the push_back Member Function You cannot use the [] operator to access a vector element that does not exist. To store a value in a vector that does not have a starting size, or is already full, use the push_back member function. Here is an example: numbers.push_back(25);

155. 155 Program 7-24 // This program stores, in two vectors, the hours worked by a specified // number of employees, and their hourly pay rates. #include #include // Needed to declare vectors using namespace std; void main(void) { vector hours; // hours is an empty vector vector payRate; // payRate is an empty vector int numEmployees; // The number of employees cout > numEmployees; cout << "Enter the hours worked by " << numEmployees; cout << " employees and their hourly rates.\n";

156. 156 Program 7-24 (continued) for (int index = 0; index > tempHours; hours.push_back(tempHours); // Add an element to hours cout > tempRate; payRate.push_back(tempRate); // Add an element to payRate } cout << "Here is the gross pay for each employee:\n"; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); for (index = 0; index < numEmployees; index++) { float grossPay = hours[index] * payRate[index]; cout << "Employee #" << (index + 1); cout << ": $" << grossPay << endl; } }

157. 157 Program 7-24 (continued) Program Output with Example Input Shown in Bold How many employees do you have? 3 [Enter] Enter the hours worked by 3 employees and their hourly rates. Hours worked by employee #1: 40 [Enter] Hourly pay rate for employee #1: 12.63 [Enter] Hours worked by employee #2: 25 [Enter] Hourly pay rate for employee #2: 10.35 [Enter] Hours worked by employee #3: 45 [Enter] Hourly pay rate for employee #3: 22.65 [Enter] Here is the gross pay for each employee: Employee #1: $505.20 Employee #2: $258.75 Employee #3: $1019.25

158. 158 Determining the Size of a vector Unlike arrays, vectors can report the number of elements they contain. This is accomplished with the size member function. Here is an example of a statement that uses the size member function: numValues = set.size(); In the statement above, assume that numValues is an int, and set is a vector. After the statement executes, numValues will contain the number of elements in the vector set.

159. 159 Determining the Size of a vector Example: void showValues(vector vect) { for (int count = 0; count < vect.size(); count++) cout << vect[count] << endl; }

160. 160 Program 7-25 // This program demonstrates the vector size // member function. #include #include using namespace std; // Function prototype void showValues(vector ); void main(void) { vector values; for (int count = 0; count < 7; count++) values.push_back(count * 2); showValues(values); }

161. 161 Program 7-25 (continued) //************************************************** // Definition of function showValues. * // This function accepts an int vector as its * // argument. The value of each of the vector's * // elements is displayed. * //************************************************** void showValues(vector vect) { for (int count = 0; count < vect.size(); count++) cout << vect[count] << endl; }

162. 162 Program 7-25 (continued) Program Output 0 2 4 6 8 10 12

163. 163 Removing Elements from a vector Use the pop_back member function to remove the last element from a vector. collection.pop_back(); The statement above removes the last element from the collection vector.

164. 164 Program 7-26 // This program demosntrates the vector size member function. #include #include using namespace std; void main(void) { vector values; // Store values in the vector values.push_back(1); values.push_back(2); values.push_back(3); cout << "The size of values is " << values.size() << endl; // Remove a value from the vector cout << "Popping a value from the vector...\n"; values.pop_back(); cout << "The size of values is now " << values.size() << endl;

165. 165 Program 7-26 (continued) // Now remove another value from the vector cout << "Popping a value from the vector...\n"; values.pop_back(); cout << "The size of values is now " << values.size() << endl; // Remove the last value from the vector cout << "Popping a value from the vector...\n"; values.pop_back(); cout << "The size of values is now " << values.size() << endl; } Program Output The size of values is 3 Popping a value from the vector... The size of values is now 2 Popping a value from the vector... The size of values is now 1 Popping a value from the vector... The size of values is now 0

166. 166 Clearing a vector To completely clear the contents of a vector, use the clear member function. Here is an example: numbers.clear(); After the statement above executes, the numbers vector will be cleared of all its elements.

167. 167 Program 7-27 // This program demosntrates the vector size member function. #include #include using namespace std; void main(void) { vector values(100); cout << "The values vector has “ << values.size() << " elements.\n"; cout << "I will call the clear member function...\n"; values.clear(); cout << "Now, the values vector has “ << values.size() << " elements.\n"; }

168. 168 Program 7-27 (continued) Program Output The values vector has 100 elements. I will call the clear member function... Now, the values vector has 0 elements.

169. 169 Detecting an Empty vector To determine if a vector is empty, use the empty member function. The function returns true if the vector is empty, and false if the vector has elements stored in it. Here is an example of its use: if (set.empty()) cout << "No values in set.\n";

170. 170 Program 7-28 // This program demosntrates the vector's empty member function. #include #include using namespace std; // Function prototype float avgVector(vector ); void main(void) { vector values; int numValues; float average; cout > numValues;

171. 171 Program 7-28 (continued) for (int count = 0; count > tempValue; values.push_back(tempValue); } average = avgVector(values); cout << "Average: " << average << endl; } //************************************************************* // Definition of function avgVector. * // This function accepts an int vector as its argument. If * // the vector contains values, the function returns the * // average of those values. Otherwise, an error message is * // displayed and the function returns 0.0. * //*************************************************************

172. 172 Program 7-28 (continued) float avgVector(vector vect) { int total = 0;// accumulator float avg;// average if (vect.empty())// Determine if the vector is empty { cout << "No values to average.\n"; avg = 0.0; } else { for (int count = 0; count < vect.size(); count++) total += vect[count]; avg = total / vect.size(); } return avg; }

173. 173 Program 7-28 (continued) Program Output with Example Input Shown in Bold How many values do you wish to average? Enter a value: 12 Enter a value: 18 Enter a value: 3 Enter a value: 7 Enter a value: 9 Average: 9 Program Output with Example Input Shown in Bold How many values do you wish to average? 0 No values to average. Average: 0

174. 174 Summary of vector Member Functions Member FunctionDescription at(element) Returns the value of the element located at element in the vector. Example: x = vect.at(5); The statement above assigns the value of the 5 th element of vect to x. capacity() Returns the maximum number of elements that may be stored in the vector without additional memory being allocated. (This is not the same value as returned by the size member function). Example: x = vect.capacity(); The statement above assigns the capacity of vect to x.

175. 175 Summary of vector Member Functions clear() Clears a vector of all its elements. Example: vect.clear(); The statement above removes all the elements from vect. empty() Returns true if the vector is empty. Otherwise, it returns false. Example: if (vect.empty()) cout << "The vector is empty."; The statement above displays the message if vect is empty. pop_back() Removes the last element from the vector. Example: vect.pop_back(); The statement above removes the last element of vect, thus reducing its size by 1.

176. 176 Summary of vector Member Functions push_back(value) Stores a value in the last element of the vector. If the vector is full or empty, a new element is created. Example: vect.push_back(7); The statement above stores 7 in the last element of vect. reverse() Reverses the order of the elements in the vector (the last element becomes the first element, and the first element becomes the last element.) Example: vect.reverse(); The statement above reverses the order of the element in vect. resize(elements, value) Resizes a vector by elements elements. Each of the new elements is initialized with the value in value. Example: vect.resize(5, 1); The statement above increases the size of vect by 5 elements. The 5 new elements are initialized to the value 1.

177. 177 Summary of vector Member Functions swap(vector2) Swaps the contents of the vector with the contents of vector2. Example: vect1.swap(vect2); The statement above swaps the contents of vect1 and vect2.