231121 모두 0으로 만들기

private int[] visit;
private long[] temp;
private ArrayList<Integer>[] adj;
private long answer;

public long solution(int[] a, int[][] edges) {
	int sum = 0;
	int n = a.length;
	visit = new int[n];
	adj = new ArrayList[n];
	temp = new long[n];
	answer = 0;

	for (int i = 0; i < n; i++) {
		adj[i] = new ArrayList<>();
		sum += a[i];
		temp[i] = a[i];
	}

	if (sum != 0) {
		return -1;
	}

	buildGraph(edges);

	dfs(0);

	return answer;
}

private void buildGraph(int[][] edges) {
	for (int i = 0; i < edges.length; i++) {
		int u = edges[i][0];
		int v = edges[i][1];
		adj[u].add(v);
		adj[v].add(u);
	}
}

private long dfs(int i) {
	visit[i] = 1;
	for (int j = 0; j < adj[i].size(); j++) {
		int next = adj[i].get(j);
		if (visit[next] == 0) {
			temp[i] += dfs(next);
		}
	}
	answer += Math.abs(temp[i]);
	return temp[i];
}

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