C language loop structure program

while loop 、do while loop 、for loop 、break End 、continue end

Environmental Science ：CentOS7;
The loop condition ：① The loop body ;② Cycle end condition ;
characteristic ： The computer only deals with conditional loops （ effectiveness 、 Certainty and finiteness ）.

• while loop （ First judge recycling , Embedded statement ）
  Example 1：1+2+3+…+100
  

#include <stdio.h>
int main() {
    
    int i, sum = 0;
    i = 1;
    while (i <= 100) {
    
          sum += i;
          i++;
    }
    printf ("%d\n",  sum);
    return 0;
}
[[email protected] c]# gcc -o while while.c
[[email protected] c]# ./while
5050

• do while（ First cycle, then judge ）
  Example 1：1+2+3+…+100
  

#include <stdio.h>
int main() {
    
    int i,  sum = 0;
    i = 1;
    do {
    
          sum += i;
          i++;
    }
    while (i <= 100);
    printf ("%d\n",  sum);
    return 0;
}
[[email protected] c]# gcc -o dowhile1 dowhile1.c
[[email protected] c]# ./dowhile1
5050

• for loop （ Assign an initial value to a loop variable ; The loop condition ; Loop variable increment ）

#include <stdio.h>
int main() {
    
    int i, sum = 0;
    for (i = 1; i <= 100; i++)
        {
    
        sum += i;
        }
    printf("%d\n", sum);
    return 0;
}

[[email protected] c]# gcc -o for for.c
[[email protected] c]# ./for
5050

• break sentence （ End the cycle ahead of time , Terminate the entire ）
  Example ： The current shift does not exceed 30 people , Make the program count the average score of the class , End the loop when a negative number is received .

[[email protected] c]# cat break.c
#include <stdio.h>
int main() {
    
    float score, sum = 0, average;
    int i, n;
    for (i = 1; i < 31; i ++) {
    
        scanf ("%f", &score);
        if (score < 0) break;
        sum = sum + score;
        }
     n = i - 1;
     average = sum/n;
     printf ("n = %d, average = %7.2f\n", n, average);
     return 0;
}
[[email protected] c]# ./break
77
88
99
12
33
44
55
66
-1
n = 8, average =   59.25

#flloat score Define a floating point variable score
#%7.2f Print before the decimal point 7 position （ Less than seven places are filled in 0); Two decimal places （ Less than two people make up for it 0）.

• continue sentence （ End this cycle ahead of time , Just terminate this cycle, not the whole ）
  PS： End this cycle , That is, skip the following unexecuted statements in the loop body , Then proceed to the next time whether 1 Execute loop judgment .
  Example ： Enter the grade of all the students in a class , Output the results of failed students , And ask for the average score of passing students .

#include <stdio.h>
int main() {
    
    float score, sum = 0, average;
    int i, n = 0;
    for (i = 1; i < 6; i ++) {
      # Suppose that those who fail have 5 individual 
        printf ("please enter score:");
        scanf ("%f", &score);
        if (score < 60) {
       # If you fail 
            printf ("Fail:%7.2f\n", score); # End this cycle , Output failing grades 
            continue;
            }
         sum = sum + score;
         n = n + 1;   # Count the number of people who failed 
         }
     average = sum/n;  # A passing grade average 
     printf ("\n n = %d, average = %7.2f\n", n,  average);  # Output the number of passing students and average score 
     return 0;
}
[[email protected] c]# gcc -o continue continue.c
[[email protected] c]# ./continue
please enter score:44
Fail:  44.00
please enter score:55
Fail:  55.00
please enter score:60
please enter score:70
please enter score:90

 n = 3, average =   73.33