在do while循环中跳过给定值时进行ac迭代

Question

I have a very simple problem in C. I am trying to write a simple program that outputs multiples of 10 between 10 and 100 , inclusive (ie: on the closed interval [10,100] ) that skips 30 and 70 and outputs the values vertically.

Here is my code:

#include<stdio.h>
main()
{
  int i=10;
  do {
    if(i==30||i==70)
      continue; 

    printf("\n %d",i);
    i++;
  } while(i<100);

  return 0;
}

The program stops at 29 skips 30 and continues into a never ending loop. What is wrong?

Answer 1

The problem is that when you hit the if statement, you are now skipping the increment of i . So you never reach 100!

#include<stdio.h>
main()
{
  int i=10;
  do {
    if(i==30||i==70)
      continue;        //!!!! This will skip the i increment

    printf("\n %d",i);
    i++;
  } while(i<100);

  return 0;
}

I recommend a for loop:

main()
{
  for (i = 10; i < 100; i++) {
    if(i==30||i==70)
      continue;          // The for loop will do the i++ on the "continue"

    printf("\n %d",i);
  } 

  return 0;
}

Answer 2

mbratch correctly pointed out your problem, but you might want to consider a for loop for this sort of thing. It would have prevented this particular problem, since the increment is automatic.

I won't do the whole thing for you, since you're obviously trying to learn, but this ought to get you started:

for (i=0; i<100; i+= 1)

You'll have to change some of the numbers in that line, but hopefully you'll understand what they mean when you change them.

Answer 3

When i reaches 30 the continue statements moves back to the start of the loop.

And so the loop continues endlessly as i is not incremented from this point.

Answer 4

Your code's doing exactly what it's written to do. The continue skips the increment instruction, so the value hits 30 and gets stuck there. Move the increment to the start of the loop body, or better yet, use a for instead of a while .

Answer 5

It loops forever because you continue but don't increment i.

if(i==30||i==70) {
  i++;
  continue;   
}

or you could use a for loop like so,

#include<stdio.h>
int main()
{ 
  int i=10;

  for (; i < 100; i++)
  {
    if(i==30 || i==70) {
      continue;
    }
    printf("\n %d",i);
  }

  return 0;
}

Answer 6

The reason is that i is never incremented after 30 inside the body of do..while. You'd need to increment it.

if (i == 30 || i == 70){
    i++;
    continue;
}

Answer 7

Don't use continue . Instead print out the value as long as != to 30 and 70 . Also iterate by 10 instead of 1 to output multiples 10 .

#include<stdio.h>
main()
{
    int i = 10;

    do
    {
        if (i != 30 && i != 70)
            printf("\n %d", i);

        i += 10;

    }
    while (i <= 100); // if you want to print 100

    return 0;
}

Output:

 10
 20
 40
 50
 60
 80
 90
100

Use while (i <= 100); if you need to also print 100 .