abc328f 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>;

int main(int argc, char **argv)
{
    int n, q;
    cin >> n >> q;
    vl xs(n + 1);
    vi fa(n + 1, -1);
    function<int(int)> ufind = [&](int x) {
        if (fa[x] == -1)
            return x;
        int &pa = fa[x];
        int nf = ufind(pa);
        xs[x] += xs[pa];
        return pa = nf;
    };
    auto ujoin = [&](int x, int y, ll w) {
        int fx = ufind(x), fy = ufind(y);
        if (fx == fy) {
            dbg(x, y, xs[x], xs[y], w, fx);
            return xs[x] == xs[y] + w;
        }
        xs[fy] = -xs[y] + xs[x] - w;
        // xs[fy] = -xs[y] + xs[x] + w; why not + w?
        fa[fy] = fx;
        return true;
    };
    vector<int> ans;
    for (int i = 0, a, b, d; i < q; ++i) {
        cin >> a >> b >> d;
        if (ujoin(a, b, ll(d)))
            ans.push_back(i + 1);
    }
    for (auto x : ans)
        cout << x << ' ';
    cout << endl;
    return 0;
};