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;
 };