MinStack

leetcode Min Stack

 

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 {

    private Stack<Integer> stack;

    private Stack<Integer> min;  //存储最小数的栈



    public MinStack() {

        stack = new Stack<Integer>();

        min = new Stack<Integer>();

    }



    public void push(int x) {

        

        if (min.isEmpty() || min.peek()>=x)

            min.push(x);

        stack.push(x);

    }



    public void pop() {

        if (stack.peek().equals(min.peek()))

            min.pop();

        stack.pop();

    }



    public int top() {

        return stack.peek();

    }



    public int getMin() {

        return min.peek();

    }

}