Computer Science III WEEK4 Dr.Elgin KILIÇ

Transcription

1 Computer Science III LOOPS FOR LOOP STATEMENT WEEK4 Dr.Elgin KILIÇ A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. Syntax The syntax of a for loop in C programming language is: for ( initial; condition; increment ) { statement(s); for ( i=0; i<10; i++ ) { procese(s), statement(s);

2 Here is the flow of control in a for loop: 1. The initial step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears. 2. Next, the condition is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and the flow of control jumps to the next statement just after the for loop. 3. After the body of the for loop executes, the flow of control jumps back up to the increment statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the condition. Example1: #include <stdio.h> { int a,b; for( /*int*/ a = 10; a < 20; a = a + 1 ) {printf("value of a: %d \n", a); for(b = 30; b < 40; b++ ) {printf("value of b: %d \n", b); printf("value of b++: %d \n", b++); return 0;

3 Example2: #include <stdio.h> { int b; for( int a = 10; a < 20; a = a + 1 ) {printf("value of a: %d \n", a); for(b = 30; b < 40; b++ ) {printf("value of b: %d \n", b); /* printf("value of b++: %d \n", b++); */ return 0; Example3: #include <stdio.h> { int b; for( int a = 20; a > 10; a-- ) {printf("value of a: %d \n", a); for(b = 40; b > 30; b-- ) {printf("value of b: %d \n", b); /* printf("value of b--: %d \n", b--); */ return 0;

4 /*Example5: Find the average temperature of a city that have been measured for 10 days.*/ #include <stdio.h> { int i,temp,sum=0; for( i = 1; i <= 10; i++ ) {printf(" \n Enter temp. of i: %d day = ", i); scanf( %d,&temp); sum+=temp; /*sum=sum+temp;*/ printf( Average temp is=%f,(float)sum/i); return 0; Let s use decreasing structure; #include <stdio.h> { int i,temp,sum=0; for( i = 10; i>= 1; --i ) {printf("\n Enter temp. of i: %d day", 11-i); scanf( %d,&temp); sum+=temp; /*sum=sum+temp;*/ printf( \n sum=%d,sum); printf( Average temp=%f,(float)sum/10); return 0;

5 #include <stdio.h> { int k,i,temp,sum=0; for( i = 10; i>= 1; --i ) {k=i; --k; printf( \n k=%d,k); printf("\n Enter temp. of i: %d day", 11-i); scanf( %d,&temp); sum+=temp; /*sum=sum+temp;*/ printf( Average temp=%f,(float)sum/10); return 0;

6 NESTED FOR LOOPS for(ini1;case1;step1) { for(ini2;case2;step2) { for(ini3;case3;step3).. {. /*Example: The daily temperatures of 4 cities are measures for 3 days. Find the Daily average temperature within cities. */ Days Cities City1 city2 city3 City4 Average ? ? ?

7 #include<stdio.h> int main() {int day,city,sum,temp; for(day=1;day<=3;day++) { printf( \n Enter temps for %d,day); sum=0; for(city=1;city<=4;city++) { printf( \n Enter %d city,city); printf( s temperature \n ); scanf( %d,&temp); sum+=temp; printf( Average of %d day %f,day,(float)sum/4); scanf( %d ); return 0;

8 WHILE LOOPS We use these loops commonly for undetermined number of processes or sets depending on case control. WHILE (CASE) { PROCESSES While runs whenn case is TRUE. Case must change in block otherwise loop never stops. #include <stdio.h> {int a=10,b=0,number; while( a < 21 ) {printf("value of a: %d \n", a); a++; while( b < 11 ) {printf("enter value %d. number: \n", b); b++;scanf( %d,&number); scanf( %d );return 0;

9 NESTED WHILE LOOPS WHILE (CASE1) {PROCESSES M; WHILE (CASE2) {PROCESSES 2; PROCESSES K; Example: In a company 3 types of products are sold for 30 days (4 days). The prices of products are as follows 15TL, 7TL, 9TL. The number of customers visiting the company is UNKNOWN. Any customer can buy as much as she\he wants. The data entrance is done by entering TYPE and AMOUNT of the product. Find how much are sold from each product at the end of month.

10 for (day=1; day<=30; day++) {. answer= Y ; While(answer== Y ) { answer1= Y ; While(answer1== Y ) {.. Do you want more product? Answer1 /* buying process*/ IS there another customer? answer /* customer*/. /*end of for */

11 for (day=1; day<=3; day++) {. acust=1; While(acust==1) { proans=1; While(proans==1) {.. Do you want more product? proans /* buying process*/ IS there another customer? acust /* customer*/. /*end of for */

12 Solution: #include<stdio.h> int main(); {char answer,answer1; int day,type,sum1=0,sum2=0,sum3=0,amount; for (day=1; day<=4; day++) {printf( Enter %d day s info. \n,day); answer= Y ; While(answer== Y ) { answer1= Y ; top=0; top+=amount While(answer1== Y ) { printf( Enter type and amount \n ); scanf( %d %d,&type,&amount); If (type==1) {sum1+=amount; If (type==2) {sum2+=amount; If (type==3) {sum3+=amount; Printf( Do you want more? \n );

13 scanf( %c,&answer1); /* buying process*/ Printf( Is there another customer? \n ); scanf( %c,&answer); /* customer*/. /*end of for */ Printf( %d sold from type1,sum1); Printf( %d sold from type2,sum2); Printf( %d sold from type3,sum3); Return 0;

14 do while Loop Unlike for and while loops, which test the loop condition at the top of the loop, the do...while loop in C programming checks its condition at the bottom of the loop. A do...while loop is similar to a while loop, except the fact that it is guaranteedto execute at least one time. Syntax The syntax of a do...while loop in C programming language is: do { statement(s); while( condition ); Notice that the conditional expression appears at the end of the loop, so the statement(s) in the loop executes once before the condition is tested.

15 If the condition is true, the flow of control jumps back up to do, and the statement(s) in the loop executes again. This process repeats until the given condition becomes false. Example: Find the average of negative and positive integer numbers entered from keyboard. The DATA ENTRANCE stops when number is given as 0. Use do_while to solve this. #include<stdio.h> {int i=0,j=0,n,sumneg=0,sumpos=0; do {/*printf ("\n Enter a number \ n");*/ scanf("%d",&n); if (n>0) {sumpos+=n; i++; if (n<0) {sumneg+=n;j++; while(n!=0); if (i!=0) { printf("\n Average of positive=%d",sumpos/i); if (j!=0) { printf("\n Average of negative=%d",sumneg/j); return 0;

16 #include<stdio.h> {int i=0,j=0,n,sumneg=0,sumpos=0; do {printf ( \n Enter a number \ n ); scanf( %d,&n); if (n>0) {sumpos+=n; i++ if (n<0) {sumneg+=n;j++ while(n!=0) if (i!=0) { printf( \n Average of positive=%d,sumpos/i); if (j!=0) { printf( \n Average of negative=%d,sumneg/j); return 0; Example: Calculate the following formula for given x,y,z integers entered from keyboard. The DATA ENTRANCE stops when x+y>2*z. Use do_while to solve this. WW = zz2 + yy 3 xx + 3zz Also check if x+3z not equal to 0;

17 #include<stdio.h> {int x,y,z; float w; do {printf ("\n Enter x,y,z triple \n"); scanf("%d %d %d",&x,&y,&z); if ((x+3*z)!=0) {w=(z*z+y*y*y)/(x+3*z); printf("\n x %d y %d z %d and w =%f",x,y,z,w); while((x+y)<2*z); printf("\n Data entrance stopped x y z values are =%d %d %d ",x,y,z); return 0; Example: Calculate the following formula for given a,b,c integers entered from keyboard. The DATA ENTRANCE stops when a+b+c=0. Use do_while to solve this. YY = aabb + bb cc aaaa + 2 bb

18 Average of all Y values when a>0. Average of all Y values when b<0. Max Y value when c>0 and show a,b,c numbers giving this value. #include<stdio.h> {int a,b,c,k,ma,mb,mc,i=0,j=0; float y,max,sum1=0.0,sum2=0.0; do {printf ("\n Enter a,b,c triple \n"); scanf("%d %d %d",&a,&b,&c); if ((a*b+2^b)!=0) {y=(a^b+b^c)/(a*c+2^b); if (a>0){sum1+=y;i++; if(b<0) {sum2+=y;j++; if(c>0) {k++; if(k==1) {max=y;ma=a;mb=b;mc=c; if(y>max) {max=y;ma=a;mb=b;mc=c; printf("\n a %d b %d c %d and y =%f",a,b,c,y); while((a+b+c)!=0);

19 printf("\n entrance stopped a b c values are =%d %d %d ",a,b,c); if (i!=0) {printf(" Average1 %f ",sum1/i); if (j!=0) {printf(" Average2 %f ",sum2/j); printf("max Y value %f",max); printf(" a b c giving max,%d,%d,%d ",ma,mb,mc); return 0; /*/*/*/*/*/*/*/*/* #include <stdio.h> {/* local variable definition */ int a = 10; /* do loop execution */ do { if( a == 15) {a = a + 1; continue; printf("value of a: %d\n", a); a++; while( a < 20 ); return 0;

20 */*/*/*/*/*/*/*/*/*/ The syntax for a nested do...while loop statement in C programming language is as follows: do { statement(s); do { statement(s); do { statement(s); while( conditionk ); while( condition2 ); while( condition1 );.. Statements; A final note on loop nesting is that you can put any type of loop inside any other type of loop. For example, a for loop can be inside a while loop or vice versa.

21 Example: For a given infinite set of integer numbers check how many of these numbers are prime? Write a c program to solve this. S={2,57,23,11,42, 2 is prime, 23 is prime / exact division % modula operatör A number is prime if and only if it is divisible only by 1 and itself. scanf( %d,&n); for(i=1;i<=n;i++) { remainder=n%i; if(remainder=0) {p++; if (p==2) {printf( \n %n is prime,n); Solution: #include<stdio.h> {int n,i,remainder,answer; do { scanf( %d,&n); for(i=1;i<=n;i++) { remainder=n%i; if(remainder=0) {p++; if (p==2) {printf( \n %n is prime,n); printf( \n Is there another number YES=1 N0=0? ); scanf( %d,&answer); while(answer==1); return 0;