Erase element in vector while iterating the same vector [duplicate]

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In the line:

it2 = uc.erase(it2);

an element pointed by iterator it2 is removed from the vector, elements are shifted in memory in order to fill that gap which invalidates it2. it2 gets a new value and now points to the first element after the the removed one or the end of the vector (if removed element was the last one). This means that after erasing an element you should not advance it2. An alternative to proposed remove-erase idiom is a simple trick: 

for(it2 = uc.begin(); it2 != uc.end();)
{
   ...   
   if(...)
   {
      it2 = uc.erase(it2); 
   }
   else
   {
      ++it2;
   }
   ...
}

You can read more about this here.

Edit:
Regarding your comment, you can use a flag to pass the information whether an element has been erased or not, and you can check it when you get out from the inner loop:

for(it2=uc.begin(); it2 != uc.end();)
{
   bool bErased = false;

   for(it3 = c.begin(); it3 != c.end(); ++it3)
   {
      if(adjacencyMatris[(*it2).id][(*it3).id] == 0 )
      {
         B.id = (*it2).id;
         it2 = uc.erase(it2);
         bErased = true;
         B.color = currentColor;
         c.push_back(B);
         break;
      }
   }

   if(!bErased)
      ++it2;
}

After you’ve erased an element from uc you need to break from the inner loop. In the next iteration of the outer loop you’ll be able to access the next element in the uc through a valid iterator.

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