모두 0으로 만들기 C++

https://programmers.co.kr/learn/courses/30/lessons/76503

코딩테스트 연습 - 모두 0으로 만들기

#include <string>
#include <vector>
#include <cstring>
#include <iostream>

using namespace std;
const int MAX = 300001;
int root = 0;
vector<int> map[MAX];
int visited[MAX];
long long answer = 0;
vector<long long> v;

void dfs(int parent) {

	visited[parent] = true;
	for (int i = 0; i < map[parent].size(); i++) {
		if (visited[map[parent][i]] == true) continue;

		dfs(map[parent][i]);

		answer += abs(v[map[parent][i]]);
		v[parent] += v[map[parent][i]];
		v[map[parent][i]] = 0;
	}
}

long long solution(vector<int> a, vector<vector<int>> adges) {
	memset(visited, -1, sizeof(visited));

	for (int i = 0; i < a.size(); i++) {
		v.push_back(a[i]);
	}

	for (int i = 0; i < adges.size(); i++) {
		map[adges[i][0]].push_back(adges[i][1]);
		map[adges[i][1]].push_back(adges[i][0]);
	}

	visited[0] = true;
	dfs(0);

	if (v[0] != 0) return -1;
	else return answer;
}