155. Min Stack

class MinStack {
        vector<pair<int,int>> arr;


public:
    MinStack() {
        
    }
    
    void push(int val) {
        int n=arr.size();
        if(n==0){
            arr.push_back({val,val});
        }
       else{
           int mi=min(val,arr[n-1].second);
           arr.push_back({val,mi});
       }
        
    }
    
    void pop() {
        arr.pop_back();
        
    }
    
    int top() {
        int n=arr.size();
        return arr[n-1].first;
        
    }
    
    int getMin() {
        int n=arr.size();
        return arr[n-1].second;
        
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack* obj = new MinStack();
 * obj->push(val);
 * obj->pop();
 * int param_3 = obj->top();
 * int param_4 = obj->getMin();
 */