Submission #540643

#TimeUsernameProblemLanguageResultExecution timeMemory
540643Vladth11Pipes (CEOI15_pipes)C++14
20 / 100
1780 ms65536 KiB
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define debug(x) cerr << #x << " " << x << "\n"
#define debugs(x) cerr << #x << " " << x << " "

using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <long double, pii> muchie;

const ll NMAX = 200001;
const ll VMAX = 1000001;
const ll INF = (1LL << 60);
const ll MOD = 1000000007;
const ll BLOCK = 1000000;
const ll nr_of_bits = 16;

vector <int> v[NMAX];
int root;
int dp[NMAX], lvl[NMAX];

void DFS(int node, int p){
    lvl[node] = lvl[p] + 1;
    for(auto x : v[node]){
        if(lvl[x] == 0){
            DFS(x, node);
            dp[node] += dp[x];
        }else if(lvl[x] > lvl[node]){
            dp[node]--;
        }else{
            dp[node]++;
        }
    }
    if(node != root){
        dp[node]--;
    }
    if(dp[node] == 0 && node != root){
        cout << node << " " << p << "\n";
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, m, i;
    cin >> n >> m;
    for(i = 1; i <= m; i++){
        int a, b;
        cin >> a >> b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    for(i = 1; i <= n; i++){
        if(!lvl[i]){
            root = i;
            DFS(root, 0);
        }
    }
    return 0;
}
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