C Tutorial/Statement/For statement
Содержание
- 1 Continue a for loop
- 2 for LOOP
- 3 for loop backward
- 4 indefinite loop: empty for
- 5 Initialize loop control variable outside the for statement
- 6 Nest for loop: two different control variables
- 7 Nest if statement in for loop
- 8 Omit all three parts in for loop
- 9 Sum integers in for statement
- 10 The for loop with a comma operator
- 11 Use char variable to control for loop
- 12 Use for loop to print a rectangle
Continue a for loop
<source lang="cpp">#include <stdio.h>
int main(){
int x=0;
for(;;) {
x++;
if(x<=5) {
printf("%d, ",x);
continue;
}
printf("%d is greater than 5!\n",x);
break;
}
return(0);
}</source>
1, 2, 3, 4, 5, 6 is greater than 5!
for LOOP
The for loop is usually used when the number of iterations is predetermined.
The format of the for loop is
<source lang="cpp">for (expr1;expr2;expr3){
s1;
s2 ;
}</source>
for loop backward
<source lang="cpp">#include <stdio.h> int main(void) {
long sum = 0L;
int count = 10;
int i;
for (i = count ; i >= 1 ; sum += i-- );
printf("\nTotal of the first %d numbers is %ld\n", count, sum);
return 0;
}</source>
Total of the first 10 numbers is 55
indefinite loop: empty for
<source lang="cpp">#include <stdio.h>
- include <ctype.h> /* For tolower() function */
int main(void) {
char answer = "N";
printf("\nThis program calculates the average of any number of values.");
for( ;; ) /* Indefinite loop */
{
printf("Do you want to enter another value? (Y or N): ");
scanf(" %c", &answer );
if( tolower(answer) == "n" ){
break;
}
}
return 0;
}</source>
This program calculates the average of any number of values.Do you want to enter another value? (Y o
r N): N
Initialize loop control variable outside the for statement
<source lang="cpp">#include <stdio.h> int main(void) {
int count = 1;
for( ; count <= 10 ; ++count)
printf("\n%d", count);
printf("\nWe have finished.\n");
return 0;
}</source>
1
2
3
4
5
6
7
8
9
10
We have finished.
Nest for loop: two different control variables
<source lang="cpp">#include <stdio.h> int main(void) {
long sum = 0L;
int count = 10;
int i,j;
for(i = 1 ; i <= count ; i++ ){
sum = 0L;
for(j = 1 ; j <= i ; j++ )
sum += j;
printf("\n%d\t%ld", i, sum);
}
return 0;
}</source>
1 1
2 3
3 6
4 10
5 15
6 21
7 28
8 36
9 45
10 55
Nest if statement in for loop
<source lang="cpp">#include <stdio.h> int main(void) {
int chosen = 15;
int guess = 0;
int count = 3;
printf("\nA Number.\n");
for( ; count>0 ; --count)
{
printf("\nYou have %d tr%s left.", count, count == 1 ? "y" : "ies");
printf("\nEnter a guess: ");
scanf("%d", &guess);
if (guess == chosen)
{
printf("\nYou guessed it!\n");
return 0;
}
if(guess<1 || guess > 20)
printf("between 1 and 20.\n ");
else
printf("Sorry. %d is wrong.\n", guess);
}
printf("\nYou have had three tries and failed. The number was %d\n", chosen);
return 0;
}</source>
A Number.
You have 3 tries left.
Enter a guess: 1
Sorry. 1 is wrong.
You have 2 tries left.
Enter a guess: 2
Sorry. 2 is wrong.
You have 1 try left.
Enter a guess: 3
Sorry. 3 is wrong.
You have had three tries and failed. The number was 15
Omit all three parts in for loop
<source lang="cpp">#include <stdio.h> int main() {
printf("~ to exit");
for(;;)
{
char ch=getchar();
if(ch=="~")
{
break;
}
}
}</source>
~ to exit123
~
Sum integers in for statement
<source lang="cpp">#include <stdio.h> int main(void) {
long sum = 0L;
int count = 0;
printf("\nEnter the number of integers you want to sum: ");
scanf(" %d", &count);
for (int i = 1 ; i<= count ; sum += i++ );
printf("\nTotal of the first %d numbers is %ld\n", count, sum);
return 0;
}</source>
Enter the number of integers you want to sum: 112
Total of the first 112 numbers is 6328
The for loop with a comma operator
<source lang="cpp">#include <stdio.h> main(){
int i, j;
for (i = 0, j = 10; i < 3 && j > 8; i++, j--){
printf (" the value of i and j %d %d\n",i, j);
}
}</source>
the value of i and j 0 10
the value of i and j 1 9
Use char variable to control for loop
<source lang="cpp">#include <stdio.h> int main() {
char b,a="a" ;
for(b="A";b<"K";b++) {
printf("%d - %c ",a,b);
}
putchar("\n"); /* end of line */
return(0);
}</source>
97 - A 97 - B 97 - C 97 - D 97 - E 97 - F 97 - G 97 - H 97 - I 97 - J
Use for loop to print a rectangle
<source lang="cpp">#include <stdio.h> int main(void) {
printf("\n**************");
for(int count = 1 ; count <= 8 ; ++count)
printf("\n* *");
printf("\n**************\n");
return 0;
}</source>
**************
* *
* *
* *
* *
* *
* *
* *
* *
**************
