CODEWITHSUNDEEP
c++for-loop
acpaps
acpaps

Reputation: 23

How to exit (go to next element of parent loop) a for loop inside a for loop

for (int i = 0; i<10; i++)
{ 
  //do some validation for record length

  //if it is not valid

  continue; // goes to the next iteration in for loop for 'i'

  for (int j = 0; j<5; j+=2)    
  {

     //do some more validation for individual record

     //if it is not valid

Here it should go to the next i if i use continue. Here it will go to the next j Can anyone please let me know how to do this?

Upvotes: 2

Views: 10885

Answers (7)

IronMensan
IronMensan

Reputation: 6821

I try to avoid break and continue when dealing with loops because they are easy to miss and their meanings change if you have to restructure the code later. You can use j=5; when you need to exit the inner loop. If you add a third loop or a switch the meaning of that line doesn't change. Sometimes you will need to add if statements inside your loops testing i and j or even a new variable like bool iIsInvalid but I think that makes the control flow easier to read.

Upvotes: 0

Steve Jessop
Steve Jessop

Reputation: 279225

If you can't arrange the logic so that break in the inner loop gets straight to continuing the outer loop, then do this:

for (int i = 0; i<10; i++)
{ 
    if (!valid(i)) continue;
    for (int j = 0; j<5; j+=2)    
    {
        if (!valid(i,j)) goto continue_i;
        do_whatever_with_i_and_j()
    }
    more_stuff_here();
continue_i:
}

There, I've said it. The code is shorter, simpler, easier to read and easier to analyse than the version that sets a flag, then breaks, then immediately checks the flag again and conditionally continues.

Another option is this

void inner_loop(int i) {
    if (!valid(i)) return;
    for (int j = 0; j<5; j+=2)    
    {
        if (!valid(i,j)) return;
        do_whatever_with_i_and_j()
    }
    more_stuff_here();
}

for (int i = 0; i<10; i++)
{
    inner_loop(i);
}

Depending what the inner loop does, though, you might find yourself building quite a mechanism to give it access to whatever it's supposed to modify.

Community wiki, because this (or situations like it) has been argued so many times on SO as to practically define "subjective and argumentative".

Upvotes: 0

Isaac Fife
Isaac Fife

Reputation: 1689

for (int i = o; i<10; i++) {

}

for (int j = 0; j<5; j+=2) { break; }

"break;" will end your current j loop and go to the next i.

Upvotes: 0

Xeo
Xeo

Reputation: 131789

You need to specifically test for a flag in the outer loop if there is something after the inner loop:

for(some_outer_vars){
  bool should_skip = false;
  // ...
  for(some_inner_vars){
    // ...
    if(your_condition){
      should_skip = true;
      break;
    }
  }
  if(should_skip)
    continue;
  // ...
}

Upvotes: 2

Mahesh
Mahesh

Reputation: 34615

Place break; instead. This should get you out of the inner loop.

Upvotes: 0

Mark B
Mark B

Reputation: 96233

Using break; inside the j loop will exit the j loop completely.

But at least spend a couple minutes deciding if an alternate algorithm, approach, or termination condition could remove the need to break in the middle of a loop.

Upvotes: 2

Carl Norum
Carl Norum

Reputation: 224854

Do you have anything after the inner loop? If not, you can just use break:

for (i = 0; i < 10; i++)
{
  if (i is no good)
    continue;

  for (j = 0; j < 5; j++)
  {
     if (j is no good)
       break;
  }
}

If you do need to do something later, you can use break in combination with some other flag.

Upvotes: 1

Related Questions