【LeetCode热题100（68/100）】最小栈

题目地址：链接

思路： 栈。值val传入栈时同时，同时记录最小值min。

1. top：栈顶 val
2. getMin：栈顶 min

class MinStack {
    private stk:number[][]
    constructor() {
        this.stk = [];
    }

    push(val: number): void {
        this.stk.push([val, Math.min(this.getMin(), val)]);
    }

    pop(): void {
        this.stk.pop();
    }

    top(): number {
        let n = this.stk.length;
        return this.stk[n - 1][0];
    }

    getMin(): number {
        if(!this.stk.length) return Infinity;
        let n = this.stk.length;
        return this.stk[n - 1][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()
 */