[Luogu 3385] Bellman-Ford

/* https://www.luogu.com.cn/problem/P3385 */

// #pragma GCC target("avx2")
#pragma GCC optimize("O3", "unroll-loops")

// #include <bits/extc++.h>
// using namespace __gnu_pbds;

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

#define int long long
#define double long double
// template <typename T>
// using pbds_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
using pii = pair<int, int>;
template<typename T>
using prior = priority_queue<T, vector<T>, greater<T>>;
template<typename T>
using Prior = priority_queue<T>;

#define X first
#define Y second
#define ALL(x) (x).begin(), (x).end()
#define eb emplace_back
#define pb push_back

#define fastIO() ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define RANDOM() random_device __rd; \
                 mt19937 __gen = mt19937(__rd()); \
                 uniform_int_distribution<int> __dis(0, 1); \
                 auto rnd = bind(__dis, __gen);

const int INF = 1E9;
const int mod = 1E9 + 7;
const int maxn = 2000 + 5;

vector<pii> adj[maxn];
vector<int> minDis(maxn, INF), vis(maxn, 0);

void dfs_reach(int now) {
    vis[now] = 1;
    for (auto [x, dist] : adj[now]) {
        if (!vis[x]) dfs_reach(x);
    }
}

bool Bellman_Ford(int n) {
    dfs_reach(0);

    for (int t = 0; t < n-1; ++t) {
        for (int i = 0; i < n; ++i) {
            for (auto [x, dist] : adj[i]) minDis[x] = min(minDis[x], minDis[i] + dist);
        }
    }

    for (int i = 0; i < n; ++i) {
        for (auto [x, dist] : adj[i]) {
            if (vis[x] and minDis[x] > minDis[i] + dist) return false;
        }
    }

    return true;
}

void solve() {
    int n, m, u, v, w;
    cin >> n >> m;

    while (m--) {
        cin >> u >> v >> w, --u, --v;
        adj[u].eb(v, w);
        if (w >= 0) adj[v].eb(u, w);
    }

    if (Bellman_Ford(n)) cout << "N0\n";
    else cout << "YE5\n";
}

void init() {
    for (int i = 0; i < maxn; ++i) adj[i].clear();
    vis.assign(maxn, 0);
    minDis.assign(maxn, INF), minDis[0] = 0;
}

int32_t main() {
    fastIO();

    int t;
    cin >> t;
    while (t--) init(), solve();

    return 0;
}