AcWing 41. 包含min函数的栈

题目链接：https://www.acwing.com/problem/content/description/90/

 

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class MinStack { public:     stack<int> s1, s2;     /** initialize your data structure here. */     MinStack() {               }           void push(int x) {         s1.push(x);         if(s2.empty() || s2.top() >= x) s2.push(x);     }           void pop() {         if(s1.top() == s2.top()) s2.pop();         s1.pop();     }           int top() {         return s1.top();     }           int getMin() {         return s2.top();     } };   /**  * 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.getMin();  */