Design a stack to support push, pop, and retrieving the minimum?

element in constant time

public class MinStack {
private Stack<int> stack = new Stack<int>();
private Stack<int> minStack = new Stack<int>();

Follow on:

public void Push(int x) {

stack.Push(x);

if (minStack.Count == 0 || x <= minStack.Peek())

minStack.Push(x);

}
public void Pop() {
if (stack.Peek() == minStack.Peek())

minStack.Pop();

stack.Pop();

}
public int Top() {
return stack.Peek();
}
public int GetMin() {
return minStack.Peek();
}
}

Explanation:

Use two stacks: one normal stack, one for minimum values. When pushing a smaller or

equal value, push it on minStack; when popping, pop minStack if needed.