CF1850H AC

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#ifndef __DEBUG__
#define dbg(...) 42
#endif
template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vl = vector<ll>;
using vi = vector<int>;
using a3l = array<ll, 3>;

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

    vl fa(n + 1), offset(n + 1);
    function<pll(ll)> find = [&](ll x) {
        if (fa[x] == 0)
            return pll{x, 0};
        auto [p, dist] = find(fa[x]);
        fa[x] = p, offset[x] += dist;
        return pll{fa[x], offset[x]};
    };
    auto insert = [&](ll x, ll y, ll dist) {
        auto [px, dx] = find(x);
        auto [py, dy] = find(y);
        if (px == py)
            return;
        fa[py] = px;

        // offset[py] += dx;
        // offset[py] = offset[px] - dx - dist + dy;
        // offset[py] = -offset[px] + dx + dist - dy;
        // offset[py] = dist - dx + dy;
        offset[py] = dist + dx - dy;
    };
    auto query = [&](ll x, ll y, ll d) {
        auto [px, dx] = find(x);
        auto [py, dy] = find(y);
        if (px != py)
            return true;
        // return dx == dy + d;
        // return dx + d == dy;
        return dy - dx == d;
    };

    vector<a3l> conds(m);
    for (auto &c : conds) {
        cin >> c[0] >> c[1] >> c[2];
        if (c[0] > c[1]) {
            swap(c[0], c[1]);
            c[2] = -c[2];
        }
    }
    for (const auto &c : conds) {
        auto [a, b, d] = c;
        if (!query(a, b, d)) {
            cout << "NO" << endl;
            return;
        }
        insert(a, b, d);
        auto [fa, da] = find(a);
        auto [fb, db] = find(b);
        // assert(db - da == d);
        // assert(da - db == d);
        assert(db - da == d);
    }

    cout << "YES" << endl;
}

int main(int argc, char **argv)
{
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
};