Erasing from a list that you are nested iterating over

Question

Say you're iterating over a list using a nested for loop like this:

  for( list<Object>::iterator iter = list.begin() ; iter != list.end() ; ++iter )
  {
    for( list<Object>::iterator iter2 = list.begin() ; iter2 != list.end() ; ++iter2 )
    {
      if( iter != iter2 )
      {
        if( some other condition )
        { 
          iter2 = list.erase( iter2 ) ; 
          // uh oh! what about iter?
        }
      }
    }
  }

How can you maintain iter?

you can check the iterator validity rules here: http://stackoverflow.com/questions/6438086/iterator-invalidation-rules — Stephane Rolland, Oct 29 '12 at 16:42

score 4 · Accepted Answer · answered Oct 29 '12 at 16:44

4

list:erase only invalidates the iterators pointing to the item being erased. Since iter is not equal to iter2, you should be fine.

answered Oct 29 '12 at 16:44

Matt Kline

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Erasing from a list that you are nested iterating over

1 Answers1