牛客网-《剑指offer》-包含min函数的栈

题目：http://www.nowcoder.com/practice/4c776177d2c04c2494f2555c9fcc1e49

辅助栈

C++

class Solution {
public:
    void push(int v) {
        int m = s1.empty() ? v : this->min();
        m = m < v ? m : v;
        s1.push(v);
        s2.push(m);
    }
    void pop() {
        s1.pop();
        s2.pop();
    }
    int top() {
        return s1.top();
    }
    int min() {
        return s2.top();
    }
private:
    stack<int> s1;
    stack<int> s2;
};