Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
- push(x) -- Push element x onto stack.
- pop() -- Removes the element on top of the stack.
- top() -- Get the top element.
- getMin() -- Retrieve the minimum element in the stack.
- class MinStack { Stack<Integer> stack = new Stack<Integer>(); Stack<Integer> min = new Stack<Integer>(); public void push(int x) { stack.push(x); if(min.isEmpty() || min.peek()>=x) { min.push(x); } } public void pop() { if(!stack.isEmpty()){ int temp = stack.peek(); stack.pop(); if(temp == min.peek()) { min.pop(); } } } public int top() { return stack.peek(); } public int getMin() { return min.peek(); } }