EC_P.cpp

// Ivan Carvalho
// Solution to https://www.spoj.com/problems/EC_P/
#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
const int MAXN = 1010;
typedef pair<int, int> ii;
vector<int> grafo[MAXN];
vector<ii> pontes;
map<int, int> mapa[MAXN];
int num[MAXN], low[MAXN], n, m, TC, counter;
void dfs(int v, int p) {
    num[v] = low[v] = ++counter;
    for (int u : grafo[v]) {
        if (u == p) continue;
        if (num[u] == 0) {
            dfs(u, v);
            if (low[u] > num[v] && mapa[u][v] == 1) {
                pontes.push_back(ii(min(v, u), max(v, u)));
            }
            low[v] = min(low[v], low[u]);
        } else {
            low[v] = min(low[v], num[u]);
        }
    }
}
int main() {
    cin.tie(0);
    cout.tie(0);
    ios_base::sync_with_stdio(0);
    cin >> TC;
    for (int tc = 1; tc <= TC; tc++) {
        cin >> n >> m;
        counter = 0;
        for (int i = 1; i <= n; i++) {
            grafo[i].clear();
            num[i] = low[i] = 0;
            mapa[i].clear();
        }
        pontes.clear();
        for (int i = 1; i <= m; i++) {
            int u, v;
            cin >> u >> v;
            grafo[u].push_back(v);
            grafo[v].push_back(u);
            mapa[u][v]++;
            mapa[v][u]++;
        }
        for (int i = 1; i <= n; i++) {
            if (num[i] == 0) dfs(i, -1);
        }
        // cout << "Foi" << endl;
        cout << "Caso #" << tc << endl;
        sort(pontes.begin(), pontes.end());
        if (pontes.empty()) {
            cout << "Sin bloqueos" << endl;
        } else {
            cout << pontes.size() << endl;
        }
        for (ii par : pontes) {
            cout << par.first << " " << par.second << endl;
        }
    }
    return 0;
}