java 代码

class MinStack {


    public Stack<Integer> a;
    public Stack<Integer> c;

    /** initialize your data structure here. */
    public MinStack() {
        a = new Stack();
        c = new Stack();
    }

    public void push(int x) {
        a.push(x);
        if(c.isEmpty()){
            c.push(x);
            return;
        }
        c.push(Math.min(x,c.peek()));
    }

    //删除第一个元素
    public void pop() {
        int x = a.pop();
        while(!c.isEmpty() && x == c.peek()){
             c.pop();
        }

    }

    //返回第一个元素
    public int top() {
        return  a.peek();
    }

    public int getMin() {
        return c.peek();
    }

}