continue statement inside nested for loop

Question

I don't understand what exactly does the continue statement inside this for loop do. How is code any different if I remove it? Which lines does it skip if it's placed at the end of for loop?

int sum = 0, i, j, stop = 0;
for( i = 1; i <= 5 && !stop; i++)
{
    for( j = 1; j <= 5 ; j++)
    {
        if (j%4 == 0)
        {
            stop = 1;
            continue;
        }
        sum += i+j;
    }
}
printf("%d\n", sum);

If you run this program the sum is going to be 15, and if you comment out countinue line then it's going to be 20.

Please indent your code properly, It is very hard to read as is. — dandan78, Nov 20 '14 at 15:59
@dandan78 Formatting fixed. I myself didn't notice this due to bad formatting. Thanks all for the answers. — Firmus, Nov 20 '14 at 16:06

score 2 · Answer 1 · answered Nov 20 '14 at 16:03

The continue statement skips the remainder of the current loop. In the case of nested loops, it skips to the next iteration of the innermost loop.

In this case, if you didn't continue, you would execute sum += i+j; in every iteration, where it appears you only want it sometimes.

That being said, this is a very awkward loop to begin with. The whole stop variable is rather ill conceived from the get-go anyway.

Vlad from Moscow · Accepted Answer · 2014-11-20T16:19:04.877

2

It would be more clear if you would format the code. Let's consider the inner loop

for( j = 1; j <= 5 ; j++)
{
    if ( j % 4 == 0)
    {
        stop = 1;
        continue;
    }

    sum += i+j;
}

Thus as you see if j % 4 == 0 then statement

sum += i+j;

is skipped.

As for the code in whole then it has no any sense.:) It is a silly code.

In fact your code is equivalent to the following

int sum = 0, j;

for( j = 1; j <= 5 ; j++ )
{
    if ( j != 4 ) sum += j + 1
}

printf("%d\n", sum);

So you will get sum 2 + 3 + 4 + 6 that is equal to 15.:)

edited Nov 20 '14 at 16:19

answered Nov 20 '14 at 16:07

Vlad from Moscow

301,070
26
186
335

and the I loop has no porpoise, since it will only loop once – Mawg says reinstate Monica Nov 21 '14 at 07:49

Spikatrix · Answer 3 · 2014-11-20T16:09:24.153

The continue statement is used to start the next iteration of a loop,skipping everything in the loop,after the continue. In your case,once the execution of the program reaches the continue statement,then the next iteration of your inner loop starts,skipping whatever there was after the continue. It skips sum += i+j; as it is after the continue and the sum will not be added when j is 4 as j%4 will be 0. This is why you get 20 when you comment the continue and 15 when you uncomment it.

P.S: Your outer loop will execute only once as stop will be changed inside the if in your inner loop.

score 0 · Answer 4 · answered Nov 20 '14 at 16:03

continue causes the enclosing for loop to begin the next iteration. As a more basic example, take the following code:

for(int i = 0; i < 50; i++)
{
    if(i % 2 == 1) // If it's odd
        continue;
    printf("%d\n", i);
}

In this case, the continue statement will cause the for loop to immediately begin the next iteration if i is odd, hence this code will print the even numbers between 0 and 50.

score 0 · Answer 5 · edited May 25 '15 at 05:08

int sum = 0, i, j, stop = 0;

for( i = 1; i <= 5 && !stop; i++)
{
   for( j = 1; j <= 5 ; j++)
   {
      if (j%4 == 0)                  <===== is j divisible by 4 ?
       {
          stop = 1;                  <=== set stop flag, will continue for J loop
                                         but stop next I loop and end the routine
          continue;         <==== skip the rest of the J loop for this itteration
       }

       sum += i+j;
    }
}

printf("%d\n", sum);

http://msdn.microsoft.com/en-us/library/0ceyyskb.aspx explains the continue statement

continue statement inside nested for loop

5 Answers5