Submission #478972

#	Time	Username	Problem	Language	Result	Execution time	Memory
478972		hjc4vr	Pipes (CEOI15_pipes)	C++14	100 / 100	1264 ms	14864 KiB

pipes

#include <bits/stdc++.h>
using namespace std;
int ufds1[100005],ufds2[100005],low[100005],depths[100005];
vector<int> adj[100005];
int find(int a,int par[]){
    if (par[a]==a) return a;
    par[a] = find(par[a],par);
    return par[a];
}

void dfs(int cur,int par){
    depths[cur] = depths[par] + 1;
    low[cur] = depths[cur];
    bool check= false;
    for (auto it: adj[cur]){
        if (check == false && it==par){
            check = true;
            continue;
        }
        else{
        if (depths[it]==-1){
            dfs(it,cur);
            low[cur] = min(low[cur],low[it]);
            if (low[it]>depths[cur]){
                cout << cur << ' ' << it << '\n';
            }
        }else{
            low[cur] = min(low[cur],depths[it]);
            }
        }
    }
}


int32_t main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int n,m;cin>>n>>m;
    fill(depths,depths+100005,-1);
    for (int i=1;i<=n;++i){
        ufds1[i] = i;
        ufds2[i] = i;
    }
    for (int i=0;i<m;++i){
        int a,b;cin>>a>>b;
        int pa = find(a,ufds1), pb = find(b,ufds1);
        if (pa!=pb){
            adj[a].push_back(b);
            adj[b].push_back(a);
            ufds1[pb] = pa;
        }else{ // it is a back edge
            int ba = find(a,ufds2), bb = find(b,ufds2);
            if (ba!=bb){
                adj[a].push_back(b);
                adj[b].push_back(a);
                ufds2[bb] = ba;
            }
        }
    }
    for (int i=1;i<=n;++i){
        if (depths[i]==-1){
            dfs(i,0);
        }
    }
}
   
//
//4
//4
//2
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//4
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//2
//4
//4
//2

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10