Задача B. Мосты и компоненты

#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <map>
#include <iostream>
using namespace std;

map < pair <int, int>, bool> is_br;
map <pair <int, int>, int> is_mult;
void find_bridges(int v, int last, int self_depth, vector <vector<int>>& gr, vector <int>& depth, vector <int>& min_depth, vector <int>& color) {
    if (color[v] == 2) return;
    int self_min_depth = self_depth;
    depth[v] = self_depth;
    min_depth[v] = self_min_depth;
    color[v] = 1;
    for (int u : gr[v]) {
        if (color[u] == 0) {
            find_bridges(u, v, self_depth + 1, gr, depth, min_depth, color);//, bridges, edges
        }
        pair <int, int> ed1 = { min(v,u), max(v,u) };
        pair <int, int> ed2 = { max(v,u), min(v,u) };
        if (u != last || (u == last && is_mult[{ min(v, u), max(v, u) }] > 1)) {
            self_min_depth = min(self_min_depth, min_depth[u]);
            min_depth[v] = self_min_depth;
            if (depth[v] < min_depth[u]) {
                is_br[{ min(v, u), max(v, u) }] = true;
            }
        }
    }
    color[v] = 2;
}


void components(int v, vector <vector<int>>& gr, vector <int>& color, vector <pair<int, int>>& bridges, vector <int>& This) {
    if (color[v] == 2) return;
    color[v] = 1;
    This.push_back(v);
    for (int u : gr[v]) {
        //проверяем, что это рёбро не мост
        if (is_br[{ min(v, u), max(v, u) }] == true) continue;
        if (color[u] == 0) {
            components(u, gr, color, bridges, This);
        }
    }
    color[v] = 2;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    vector <vector<int>> gr(n + 1);
    for (int i = 1; i < m + 1; ++i) {
        int a, b;
        cin >> a >> b;
        gr[a].push_back(b);
        gr[b].push_back(a);
        is_mult[{ min(a, b), max(a, b) }]++;
    }
    vector <int> color(n + 1, 0);
    vector <pair<int, int>> bridges;
    vector <int> depth(n + 1, 1e9);
    vector <int> min_depth(n + 1, 1e9);
    for (int i = 1; i <= n; ++i) {
        if (color[i] != 0) continue;
        find_bridges(i, i, 0, gr, depth, min_depth, color);
    }
    color.assign(n + 1, 0);
    vector <int> This;
    vector <vector <int> > answer;
    for (int i = 1; i <= n; ++i) {
        if (color[i] != 0) continue;
        This.resize(0);
        components(i, gr, color, bridges, This);
        if (This.empty()) continue;
        sort(This.begin(), This.end());
        answer.push_back(This);
    }
    int num = answer.size();
    cout << num << '\n';
    for (auto x : answer) {
        for (auto y : x) cout << y << ' ';
        cout << '\n';
    }cout << '\n';
}