Question

I have a problem with queues in my program. Having one queue I would like to use this queue, only with another id. Here is what I have now:

queue<R> queue;
queue<R> queue2;
...
while (! queue2.empty() )
{
  R r = queue2.front();
  queue2.pop();
  queue.push(r);
}

But it is linear. I hope that it is possible to do it in O(1) time. I tried to use references but I failed.

Answer 1

You didn’t tell us how you “failed”, but references are really easy:

std::queue<R> queue;
std::queue<R>& queue2 = queue;

Job done.