#include"stack.h"

bool SecondFromTop(Stack *s, ItemType &item)
{
  ItemType top;

  // Pop twice
  if(!s->Pop(top))
    return false;
  if(!s->Pop(item)) {
    s->Push(top);  // Push back the first Pop if the second Pop fails
    return false;
  }

  // Restore by pushing in reverse order
  if(!s->Push(item) || !s->Push(top)) { // recall that || guarantees execution
                                        // left to right, so the order of Push
                                        // is correct here
    return false;                       // If either of the Pushes fails,
                                        // we return false to indicate that
                                        // the stack was not restored
  }
  
  return true;
}