模板题。

#include <bits/stdc++.h>
using namespace std;
#define sc(x) scanf("%lld", &x)
typedef long long ll;
const ll mn = 1e5 + 10;
ll n, m, hd[mn], cnt, w[mn];
struct edge
{
    ll to, nx, w, idx, isbridge = false;
} e[mn * 2];
ll st, dfn[mn], low[mn], dcnt, vis[mn];
vector<ll> dcc[mn]; //边双
ll order[mn];
signed main()
{
    sc(n), sc(m);
    auto adde = [&](ll u, ll v, ll w, ll idx)
    {
        e[++cnt] = {v, hd[u], w, idx};
        hd[u] = cnt;
        ::w[idx] = w;
    };
    for (ll i = 1, u, v, w; i <= m; ++i)
    {
        sc(u), sc(v), sc(w), adde(u, v, w, i), adde(v, u, w, i);
    }
    auto tarjan = [&](auto self, ll u, ll fa) -> void
    {
        dfn[u] = low[u] = ++st;
        for (ll i = hd[u]; i; i = e[i].nx)
        {
            ll v = e[i].to, idx = e[i].idx;
            if (!dfn[v])
            {
                self(self, v, u);
                low[u] = min(low[u], low[v]);
                if (dfn[u] < low[v])
                {
                    e[idx].isbridge = true;
                }
            }
            else if (v != fa)
            {
                low[u] = min(low[u], dfn[v]);
            }
        }
    };
    tarjan(tarjan, 1, 0);
    auto dfs = [&](auto self, ll u) -> void
    {
        vis[u] = true;
        for (ll i = hd[u]; i; i = e[i].nx)
        {
            ll v = e[i].to, idx = e[i].idx;
            if (!e[idx].isbridge)
            {
                dcc[dcnt].push_back(idx);
                if (!vis[v])
                {
                    self(self, v);
                }
            }
        }
    };
    for (ll i = 1; i <= n; ++i)
    {
        if (!vis[i])
        {
            ++dcnt;
            dfs(dfs, i);
        }
    }
    printf("%lld\n", dcnt);
    for (ll i = 1; i <= dcnt; ++i)
    {
        sort(dcc[i].begin(), dcc[i].end());
        dcc[i].erase(unique(dcc[i].begin(), dcc[i].end()), dcc[i].end());
        sort(dcc[i].begin(), dcc[i].end(), [&](ll u, ll v)
             { return w[u] < w[v]; });
        if (dcc[i].size() == 0)
            dcc[i].push_back(mn - 1);
    }
    w[mn - 1] = -2e9;
    for (ll i = 1; i <= dcnt; ++i)
    {
        order[i] = i;
    }
    sort(order + 1, order + 1 + dcnt, [&](ll u, ll v)
         { return w[dcc[u].front()] < w[dcc[v].front()]; });
    for (ll i = 1; i <= dcnt; ++i)
    {
        if (dcc[order[i]].front() == mn - 1)
        {
            printf("0\n");
            continue;
        }
        printf("%lld ", dcc[order[i]].size());
        for (auto j : dcc[order[i]])
        {
            printf("%lld ", w[j]);
        }
        printf("\n");
    }
    return 0;
}