155.cpp

class MinStack {
public:
    /** initialize your data structure here. */
    stack<pair<int,int>> s;
    MinStack() {
        while(!s.empty())
            s.pop();
    }
    
    void push(int x) {
        if(s.empty())
            s.push({x,x});
        else{
            s.push({x,min(x,s.top().second)});
        }
        return;
    }
    
    void pop() {
        if(!s.empty())
            s.pop();
        return;
    }
    
    int top() {
        if(s.empty())
            return -1;
        return s.top().first;
    }
    
    int getMin() {
        if(s.empty())
            return -1;
        return s.top().second;
    }
};

/**
 * 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();
 */