剑指 Offer 30. 包含min函数的栈

解题思路

题解

代码

class MinStack {
    Stack<Integer> s1;

     Stack<Integer> s2;
    /** initialize your data structure here. */
    public MinStack() {
        s1=new Stack();

        s2=new Stack();

    }
    
    public void push(int x) {
        s1.push(x);
        if(s2.isEmpty()||s2.peek()>=x) s2.push(x);
    }
    
    public void pop() {
        Integer pop=s1.pop();
        if(pop.equals(s2.peek())) s2.pop();

    }
    
    public int top() {
        return s1.peek();

    }
    
    public int min() {
        return s2.peek();

    }
}

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack obj = new MinStack();
 * obj.push(x);
 * obj.pop();
 * int param_3 = obj.top();
 * int param_4 = obj.min();
 */