1. Module8 Multi-dimensional Array
Thanawin Rakthanmanon
Create by: Aphirak Jansang
Computer Engineering Department
Kasetsart University, Bangkok THAILAND

2. Outlines
Array Review
Multi-dimensional Array

3. Do you remember how to declare Array?
Array for keeping 50 student's names
string [ ] NAME = new string[50];
Array for keeping 50 student's IDs
string [ ] ID = new string[50];
Array for keeping 50 student’s GPAs
double[ ] GPA = new double[50];

4. examples
int [] score = new int[6]; 1 2 3 4 5
score
int [] score = new int[4] {5,6,7,9}; 1 2 3
score 5 6 7 9

5. Accessing Array Elements
Supply an integer index for accessing array elements
indexes are zero-based
int [] score = new int[4]; 1 2 3
score -3 4 7
score[0] = -3;
score[2+1] = 7;
Score[3-1] = score[0]+score[3]
Console.WriteLine(score[2]); 4

6. How to find Array’s length?
By property Length 5
int [] matrix = new int[5];
Console.WriteLine(matrix.Length);
By method GetLength() 7
int [] matrix = new int[7];
Console.WriteLine(matrix.GetLength(0));

7. How to access Array's member ?
Displaying all members in Array ‘SCORE’
Finding summation of all members in Array ‘SCORE’
for (int i = 0; i< SCORE.Length; i++) {
Console.WriteLine(SCORE[i]); }
double sum = 0;
for (int i = 0; i< SCORE.Length; i++) {
sum = sum + SCORE.Length; }

8. Looping or Iteration in C#
while
Iteration
for
foreach
do…while

9. foreach
foreach is used to access all elements in an array and do some action repeatedly
foreach = “for each element in an array”
Syntax
foreach (var_declaration in array_name)
statement
// the above statement will be applied to each element in an array

10. foreach example string s = Console.ReadLine(); int count = 0;
for (int i = 0; i < s.Length; i++){
if(s[i] == 'A') count++; }
string s = Console.ReadLine();
int count = 0;
foreach (char c in s) {
if (c == 'A')
count++; }

11. Outlines
Array Review
Multi-dimensional Array

12. Multi-dimensional Array’s declaration
Syntax:
<type> [ , ] <name>;
<type> [ , , ] <name>;
Creation:
<name> = new <type>[<dim1>,<dim2>];
2 dimensions
3 dimensions
2 dimensions

13. Array Declaration Example
int [ , ] grid2;
grid2 = new int [3,2];
int [ , , ] grid3;
grid3 = new int [3, 2, 4];

14. How to find Array’s #dimension?
By property Rank 1
int [] matrix = new int[5];
Console.WriteLine(matrix.Rank); 2
int [,] matrix = new int[5,2];
Console.WriteLine(matrix.Rank);
int [,,] matrix = new int[5,2,3];
Console.WriteLine(matrix.Rank); 3