41.包含min函数的栈

class MinStack {
public:
    /** initialize your data structure here. */
    stack<int> stackValue;
    stack<int> stackmin;
    MinStack() {
        
    }
    
    void push(int x) {
        stackValue.push(x);
        if(stackmin.empty() || x <= stackmin.top())  //不要忘记单调栈为空的情况
            stackmin.push(x);
    }
    
    void pop() {
        if (stackmin.top() == stackValue.top()) stackmin.pop();//删除栈顶元素时，如果单调栈符合条件，夜要删除掉
        stackValue.pop();
    }
    
    int top() {
        return stackValue.top();
    }
    
    int getMin() {
        
        return stackmin.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();
 */