제출 #99699

#제출 시각아이디문제언어결과실행 시간메모리
99699adletPipes (CEOI15_pipes)C++17
20 / 100
344 ms8668 KiB
#include <bits/stdc++.h>
using namespace std;

const int N = 4e3 + 5;

int n, m, cnt, ok, timer, fup[N], used[N], tin[N];

vector < int > g[N];
unordered_map < int, int > mp[N];

inline void dfs(int v, int p = -1) {
    used[v] = 1;
    tin[v] = ++timer;
    fup[v] = timer;
    for (int to : g[v]) {
        if (to == p)
            continue;
        if (used[to])
            fup[v] = min(fup[v], tin[to]);
        else {
            dfs(to, v);
            fup[v] = min(fup[v], fup[to]);
            if (fup[to] > tin[v] && (ok || mp[v][to] == 1 || mp[to][v] == 1))
                cout << v << " " << to << "\n";

        }
    }
}

int main() {
    cin >> n >> m;
    if (m > 15000)
        ok = 1;
    for (int i = 1; i <= m; ++i) {
        int v, u;
        cin >> v >> u;
        g[v].push_back(u);
        g[u].push_back(v);
        if (!ok)
            mp[v][u]++;
    }
    for (int i = 1; i <= n; ++i) {
        if (!used[i]) {
            dfs(i);
        }
    }
}
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