Introduction to Data Structures CMPE231 Spring 2012 Assoc. Prof. Alexander Chefranov 1

Information and Meaning Concept of information similar to the concept of point, line, and plane in geometry is not defined formally It is possible to talk about the length of a line We can measure quantities of information The basic unit of information is the bit 2

Binary and Decimal Numbers Binary number system Ones complement notation Twos complement notation Binary coded decimal 3

Real Numbers Floating-point notation Mantissa Base Exponent 4

Data Type Integer Real number Character string Memory, Address, Value (Contents) Int x,y; Float a,b; 5

Character Strings Byte First byte size Null terminating strings 6

Abstract Data Types /*value definition*/ Abstract typedef RATIONAL; Condition Rational[1]!=0; /*operator definition*/ Abstract RATIONAL makerational(a,b) Int a,b; Precondition b!=0; Postcondition makerational[0]==a; makerational[1]=b; Abstract RATIONAL add(a,b) /*written a+b */ RATIONAL a,b; Postcondition add[1]==a[0]*b[0]; Add[0]==a[0]*b[1]+a[1]*b[0]; Abstract RATIONAL mult(a,b) /*written a*b */ RATIONAL a,b; Postcondition mult[0]==a[0]*b[0]; mult[1]==a[1]*b[1]; Abstract equal(a,b)/*written a==b */ RATIONAL a,b; Postcondition equal==(a[0]*b[1]==a[1]*b[0]); 7

Sequences as Value Definitions S= Abstract typedef > stp1; Abstract typedef stp2; Abstract typedef > stp3; 8

ADT for Varying-length Character Strings Abstract typedef > STRING; Abstract length(s) STRING s; Postcondition length==lens(s); Abstract STRING concat(s1,s2) STRING s1,s2; Postcondition concat==s1+s2; Abstract STRING substr(s1,i,j) STRING s1; Int I,j; Precondition 0<=i<len(s1); 0<=j<len(s2); Postcondition substr==sub(s1,I,j); Abstract pos(s1,s2) STRING s1,s2; Postcondition /*lastpos=len(s1)=len(s2) */ ((pos==-1)&&(for(i=0;i sub(s1,I,len(s2))))) || (pos>=0)&&(pos sub(s1,I,len(s2))))) 9

Data Types in C Int, float, char, double Short int, long int, unsigned Pointers Int *pi; Float *pf; Char *pc; Pi=(int *)pf; Int x; Pi=&x; x=*pi; *(pi+1) *pi+1 10

Parameters By value, by reference 1 x=5; 2 printf(“%d\n”,x); 3 funct(x); 4 printf(“%d\n”,x);.. 5 void funct(int y){ 6 ++y; 7 printf(“%d\n”,y); 8 } 11

Parameters (cont) 1 x=5; 2 printf(“%d\n”,x); 3 funct(&x); 4 printf(“%d\n”,x); 5 void funct(int *py){ 6 ++(*py); 7 printf(“%d\n”,*py); 8 } 12

Arrays in C One-dimensional array Int a[100]; Basic operations: extracting and storing Lower bound, Upper bound #define NUMELTS 100 Int a[NUMELTS]; For(int i=0;i<NUMELTS;a[i++]=0); 13

The Array as an ADT Abstract typedef > ARRTYPE(ub,eltype); Condition type(ub)==int; Abstract eltype extract(a,i) /* written a[i] */ ARRTYPE(ub, Eltype) a; Int I; Precondition 0<=i<ub; Postcondition extract==a i ; Abstract store(a,I,elt) /* written a[i]=elt */ ARRTYPE(ub,eltype) a; Int I; Eltype elt; Precondition 0<=i<ub; Postcondition a[i]==elt; 14

Using One-Dimensional Arrays #define NUMELTS 100 Void main(){ Int num[NUMELTS]; Int I; Int total; Float avg; Float diff; Total=0; For(i=0;i<NUMELTS;i++){ scanf(“%d”,num[i]); total+=num[i]; } Avg=(float)total/NUMELTS; Printf(“\nnumber difference”); For(i=0;i<NUMELTS;i++){ diff=num[i]-avg; printf(“\n %d %f”, num[i], diff); } Printf(“\n average= %f”,avg); } 15

Implementing One-Dimensional Arrays Int b[100]; Base address B[i] in base(b)+i*esize In C an array variable is a pointer variable Int *b does not reserve 100 elements B+I; *(b+i) Varying-sized element array: reserve a contiguous set of memory locations each of which holds an address of an element 16

Arrays as Parameters Float avg(float a[], int size){ int I; Float sum; sum=0; for(i=0;i<size;i++) sum+=a[i]; return (sum/size); } #define ARANGE 100 Float a[ARANGE];.. Avg(a, ARANGE); Array is passed by reference saving space and time 17

Character Strings in C #define STRSIZE 80 Char string[STRSIZE]; Int Strlen(char string[]){ int I; for(i=0;string[i]!=‘\0’;i++); return I; } Int strpos(char s1[],char s2[]){ int len1, len2, I,j1,j2; len1=strlen(s1); len2=strlen(s2); for(i=0;i+len2<=len1;i++) for(j1=i,j2=0;j2<=len2&&s1[j1]==s2[j2];j1++,j2++) if(j2==len2) return I; return -1; } 18

Character Strings in C (cont) Void strcat(char s1[], char s2[]){ int I,j; for(i=0;s1[i]!=‘\0’;i++); for(j=0;s2[j]!=‘\0’;s1[i++]=s2[j++]; } Void substr(char s1[],int I, int j, char s2[]){ int k,n; for(k=I,m=0;m<j;s2[m++]=s1[k++]; s2[m]=‘\0’; } 19

Two-Dimensional Arrays Int a[3][5]; Range r1 of the 1 st dimension (rows) is 3 Range r2 of the 2 nd dimension (columns) is 5 A[1][3]=5; Base(ar)+(i1*r2+i2)*esize 5 20

Multi-Dimensional Arrays Int b[3][2][4]; Base(ar)+esize*(i1*r2*..*rn+i2*r3*..*rn+..+i(n- 1)*rn+in) B[0][0][0] B[0][0][1] B[0][0][2] B[0][0][3] B[0][1][0] B[0][1][1] B[0][1][2] B[0][1][3] 21

Structures in C Struct{ char first[10]; char midinit; char last[20]; } sname, ename; Typedef struct{ char first[10]; char midinit; char last[20]; } NAMETYPE; NAMETYPE sname, ename; struct nametype{ char first[10]; char midinit; char last[20]; } Struct nametype sname, ename; Printf(“%s”, sname.first); Ename.midinit=‘N’; For(i=0;i<20;i++) sname.last[i]=ename.last[i]; 22

Unions #define LIFE 1 #define AUTO 2 #define HOME 3 Struct addr{ char street[50]; char city[10]; char state[3]; char zip[6]; } Struct date{ int month; int day; int year; } Struct policy{ int polnumber; Char name[30]; struct addr address; int amount; Float premium; Int kind; /*LIFE,AUTO,HOME*/ Union{ struct{ char beneficiary[30]; struct day birthday; } life; struct{ int autodeduct; Char license[10]; char state[3]; char model[15]; int year} auto; Struct{ int homededuct; int yearbuilt; } home; }policyinfo; } Struct policy p; If(p.kind==LIFE) printf(“\n%s %2d %2d %4d”, p.policyinfo.life.beneficiary, p.policyinfo.birthday.month, p.policyinfo.life.birthday.day, p. policyinfo.life.birthday.year); Struct policy a[100]; For(i=0;i<100;i++) if(a[i].kind==LIFE).. 23

Structure Parameters Int writename(struct nametype *name){ int count,I; count=0; printf(“\n”); for(i=0;(i first[i]!=‘\0’);i++){ printf(“%c”,name->first[i]); count++; } printf(“%c”,’ ‘); count++; if(name->midinit!=‘ ‘){ printf(“%c%s”, name->midinit,”. “); count+=3; } for(i=0;(i last[i])!=‘\0’);i++){ printf(“%c”,name->last[i]); count++; } return count; } 24

Allocation of Storage and Scope of Variables Automatic variables (declared within a function) Can be referenced only throughout entire block unless the variable identifier is redeclared within an internal block External variables (declared outside of any function) The scope lasts from the point at which it is declared until the end of its containing source file 25

Allocation of Storage and Scope of Variables File1 #define MAXSTUDENTS.. int grades[MAXSTUDENTS]; End of file1 File2 extern int grades[]; Float average(){.. } End file2 Static variables Register variables Uninitialized external and static variables are initialized to 0, whereas uninitialized automatic and register variables have undefined values 26

Source file1.c 1 int x,y,z; 2 void func1(){ 3 int a,b; 4 x=1; y=2;z=3;a=1;b=2; 5 printf(“%d %d %d %d %d\n”,x,y,z,a,b); 6} 7 void func2(){ 8 int a=5; 9 printf(“%d %d %d %d\n”,x,y,z,a); 10} End of file1.c 27

file2.c 11 #include 12 extern int x,y,z; 13 void main(){ 14 func1(); 15 printf(“%d %d %d\n”,x,y,z); 16 func2(); 17 func3(); 18 func3(); 19 func4(); 20 printf(“%d %d %d\n”,x,y,z); 21} 22 Void func3(){ 23 static int b; 24 y++; b++ 25 printf(“%d %d %d %d\n”,x,y,z,b); 26} 27 void func4(){ 28 int x=10,y=20,z=30; 29 printf(“%d %d %d\n”,x,y,z); 30} 28

Dynamic Memory Allocation Void *calloc(size_t nobj, size_t size) Returns a pointer to space for an array of nobj objects, each of size size, or NULL if the request cannot be satisfied. The space is initialized to zero bytes Void *malloc(size_t size) Returns a pointer to space for an object of size size, or NULL if the request cannot be satisfied. The space is uninitialized. 29