#include<bits/stdc++.h>
using namespace std;

const int maxn = 50005;
const int inf = 2147483647;
int n, m, p;
int dis[maxn], vis[maxn], head[maxn], cnt[maxn];
struct Edge {
	int nxt, to, dis;
} edge[maxn];

//链式向前星加边函数
void add(int u, int v, int w) {
	edge[++p].nxt = head[u];
	edge[p].to = v;
	edge[p].dis = w;
	head[u] = p;
}

//SPFA判断负环
bool SPFA() {
	queue<int> q;
	for (int i = 1; i <= n; i++) {
		dis[i] = inf;
		vis[i] = 0;
	}
	q.push(0);
	dis[0] = 0;
	vis[0] = 1;
	cnt[0] = 1;
	while (!q.empty()) {
		int u = q.front();
		q.pop();
		vis[u] = 0;
		for (int i = head[u]; i; i = edge[i].nxt) {
			int v = edge[i].to;
			if (dis[v] > (long long)dis[u] + edge[i].dis) {
				dis[v] = dis[u] + edge[i].dis;
				if (vis[v] == 0) {
					vis[v] = 1;
					q.push(v);
					cnt[v]++;
					if (cnt[v] > n + 1)
						return 1;
				}
			}
		}
	}
	return 0;
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int u, v, w;
		cin >> u >> v >> w;
		add(v, u, w);//转化为图论题目
	}
	for (int i = 1; i <= n; i++) {
		add(0, i, 0);//添加源点0
	}
	if (!SPFA()) {
		for (int i = 1; i <= n; i++) {
			printf("%d ", dis[i]);
		}
	} else cout << "NO" << endl;
	return 0;
}

样例本地输出为：

0 -2 0

明显与样例不符，洛谷在线 IDE 也给出了一样的结果，所以是为什么？