Retrieving the Min element in a stack in O(1) Time

Question

The reason I\'m asking this question is because I cannot see why the way I think cannot be applied to this particular question

\"How would you design a stack which,

Answer 1

I found this solution here

struct StackGetMin {
  void push(int x) {
    elements.push(x);
    if (minStack.empty() || x <= minStack.top())
      minStack.push(x);
  }
  bool pop() {
    if (elements.empty()) return false;
    if (elements.top() == minStack.top())
      minStack.pop();
    elements.pop();
    return true;
  }
  bool getMin(int &min) {
    if (minStack.empty()) {
      return false;
    } else {
      min = minStack.top();
      return true;
    }
  }
  stack elements;
  stack minStack;
};