Changing a for loop to a while loop doesn't work correctly (simple code)

Question

I want this output:

Insert a integer: 13
13
14
16
17
19

Using a for loop, it works fine:

for( ; ; num++)
{
    if (num%3==0)
        continue;
    else
        if(num%10==0)
            break;

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

But when I try change to a while loop:

while(1)
{
    if (num%3==0)
        continue;
    else
        if(num%10==0)
            break;

    printf("%d\n", num);
    num++;
}

Something strange happens:

Insert a integer: 13
13
14

Can you guys help me, please?

Answer 1

You should add num++ when changing for to while loop:

while(1)
{
    if (num%3==0) {
        num++; /* <- add this */

        continue;
    }
    else
        if(num%10==0)
            break;

    printf("%d\n", num);
    num++;
}

two increments num++ in one loop look ugly, so you'll probably want to redesign the loop into

while (num % 10 != 0) {
  if (num % 3 != 0) 
    printf("%d\n", num);

  num++;
}

Answer 2

Add the num++ line at the start of your code (while loop). As when the loop reaches num%3==0 , it keeps on re-iterating.

num--;

while(1)
{
    num++;
    if (num%3==0)
        continue;
    else
        if(num%10==0)
            break;

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

Answer 3

Use the below code

Do
{    
    if (num%3==0)
        continue;
    else
        if(num%10==0)
            break;

    printf("%d\n", num);
   }while(num++);