题目

代码

class MinStack {
    /** initialize your data structure here. */
    private Stack<Integer> stackMin;  //维护一个最小栈
    private Stack<Integer> stackPush; //维护一个压入栈
    public MinStack() {
        this.stackMin = new Stack<>();
        this.stackPush = new Stack<>();
    }
    public void push(int x) {
        stackPush.push(x);  //压入栈 一定入栈
        if(stackMin.isEmpty()) {  //最小栈为空无需判断，直接压入
            stackMin.push(x);
        } else {
            if(x <= stackMin.peek()) {
                stackMin.push(x); // 判断最小栈 栈顶元素 与 新压入的关系
            }
        }
    }
    public void pop() {
        int top = stackPush.pop();
        if(top == stackMin.peek()) {
            stackMin.pop();
        }
    }
    public int top() {
        return stackPush.isEmpty() ? 0 : stackPush.peek();
    }
    public int min() {
        return stackMin.isEmpty() ? 0 : stackMin.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();
 */

class MinStack {
    /** initialize your data structure here. */
    private Stack<Integer> stackMin;
    private Stack<Integer> stackPush;
    public MinStack() {
        this.stackMin = new Stack<>();
        this.stackPush = new Stack<>();
    }
    public void push(int x) {
        stackPush.push(x);
        if(stackMin.isEmpty()) {
            stackMin.push(x);
        } else {
            if(x <= stackMin.peek()) {
                stackMin.push(x);
            }
        }
    }
    public void pop() {
        if (! stackPush.isEmpty()) {
            if(stackPush.pop().equals(stackMin.peek())) {
                stackMin.pop();
            }
        }
    }
    public int top() {
        if(stackPush.isEmpty()) {
            return 0;
        }else return stackPush.peek();
    }
    public int min() {
        if(stackMin.isEmpty()) {
            return 0;
        }else return stackMin.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();
 */