Introduction to Data Structures

CMPE231 Spring 2012Assoc. 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 <integer,integer> 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=<s0,s1,…,sn-1>

• Abstract typedef <<tp>> stp1;• Abstract typedef <tp0,tp1,…,tpn> stp2;• Abstract typedef <<tp,n>> stp3;

8

ADT for Varying-length Character Strings

• Abstract typedef <<char>> 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<=lastpos;i++)(s2<>sub(s1,I,len(s2)))))|| (pos>=0)&&(pos<=lastpos)&&(s2==sub(s1,pos,len(s2))&&(for(i=1;i<pos;i++)(s2<>sub(s1,I,len(s2)))))

9

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

10

ParametersBy value, by reference1 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 arrayInt a[100];Basic operations: extracting and storingLower bound, Upper bound#define NUMELTS 100Int a[NUMELTS];For(int i=0;i<NUMELTS;a[i++]=0);

13

The Array as an ADTAbstract typedef <<eltype,ub>> 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==ai;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 100Void 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 addressB[i] in base(b)+i*esizeIn C an array variable is a pointer variableInt *b does not reserve 100 elementsB+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 ParametersFloat 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 100Float a[ARANGE];..Avg(a, ARANGE);Array is passed by reference saving space and time

17

Character Strings in C#define STRSIZE 80Char 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 1st dimension (rows) is 3Range r2 of the 2nd dimension (columns) is 5A[1][3]=5;Base(ar)+(i1*r2+i2)*esize

20

Multi-Dimensional Arrays

Int b[3][2][4];Base(ar)+esize*(i1*r2*..*rn+i2*r3*..*rn+..+i(n-

1)*rn+in)0 2

0 1

0 3

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 CStruct{ 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 3Struct 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 ParametersInt writename(struct nametype *name){ int count,I; count=0; printf(“\n”); for(i=0;(i<10)&&(name->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<20)&&(name->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 file1File2 extern int grades[];Float average(){..}End file2Static variablesRegister variablesUninitialized external and static variables are initialized to 0, whereas

uninitialized automatic and register variables have undefined values

26

Source file1.c1 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.c11 #include <stdio.h>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