README.md

155. 最小栈

English Version

题目描述

设计一个支持 push ，pop ，top 操作，并能在常数时间内检索到最小元素的栈。

• push(x) —— 将元素 x 推入栈中。
• pop() —— 删除栈顶的元素。
• top() —— 获取栈顶元素。
• getMin() —— 检索栈中的最小元素。

 

示例:

输入：
["MinStack","push","push","push","getMin","pop","top","getMin"]
[[],[-2],[0],[-3],[],[],[],[]]

输出：
[null,null,null,null,-3,null,0,-2]

解释：
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin();   --> 返回 -3.
minStack.pop();
minStack.top();      --> 返回 0.
minStack.getMin();   --> 返回 -2.

 

提示：

• pop、top 和 getMin 操作总是在 非空栈 上调用。

解法

“辅助栈”实现。

Python3

class MinStack:

    def __init__(self):
        """
        initialize your data structure here.
        """
        self.s = []
        self.mins = [float('inf')]

    def push(self, val: int) -> None:
        self.s.append(val)
        self.mins.append(min(self.mins[-1], val))

    def pop(self) -> None:
        self.s.pop()
        self.mins.pop()

    def top(self) -> int:
        return self.s[-1]

    def getMin(self) -> int:
        return self.mins[-1]


# Your MinStack object will be instantiated and called as such:
# obj = MinStack()
# obj.push(val)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()

Java

class MinStack {
    private Deque<Integer> s;
    private Deque<Integer> mins;

    /** initialize your data structure here. */
    public MinStack() {
        s = new ArrayDeque<>();
        mins = new ArrayDeque<>();
        mins.push(Integer.MAX_VALUE);
    }

    public void push(int val) {
        s.push(val);
        mins.push(Math.min(mins.peek(), val));
    }

    public void pop() {
        s.pop();
        mins.pop();
    }

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

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

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

C++

class MinStack {
private:
    stack<int> s;
    stack<int> mins;

public:
    /** initialize your data structure here. */
    MinStack() {
        mins.push(INT_MAX);
    }

    void push(int val) {
        s.push(val);
        mins.push(min(mins.top(), val));
    }

    void pop() {
        s.pop();
        mins.pop();
    }

    int top() {
        return s.top();
    }

    int getMin() {
        return mins.top();
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack* obj = new MinStack();
 * obj->push(val);
 * obj->pop();
 * int param_3 = obj->top();
 * int param_4 = obj->getMin();
 */

JavaScript

/**
 * initialize your data structure here.
 */
var MinStack = function () {
    this.s = [];
    this.mins = [Infinity];
};

/**
 * @param {number} val
 * @return {void}
 */
MinStack.prototype.push = function (val) {
    this.s.push(val);
    this.mins.push(Math.min(this.mins[this.mins.length - 1], val));
};

/**
 * @return {void}
 */
MinStack.prototype.pop = function () {
    this.s.pop();
    this.mins.pop();
};

/**
 * @return {number}
 */
MinStack.prototype.top = function () {
    return this.s[this.s.length - 1];
};

/**
 * @return {number}
 */
MinStack.prototype.getMin = function () {
    return this.mins[this.mins.length - 1];
};

/**
 * Your MinStack object will be instantiated and called as such:
 * var obj = new MinStack()
 * obj.push(val)
 * obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.getMin()
 */

...