[Programmers] 쇠 막대기

#include <string>
#include <vector>
#include <stack>
#include <iostream>
#define p pair<int,int>
using namespace std;

int solution(string arrangement) {
    int answer = 0;
    stack<p> s;
    int size = (int) arrangement.size();
    for(int i=0; i<size; i++){
        if(arrangement[i] == '('){
            s.push(p(i,1));
        }
        else{
            if(s.top().first == i-1){
                s.pop();
                answer += s.size();
            }
            else{
                s.pop();
                answer += 1;
            }
        }
    }
    
    return answer;
}