This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define speed ios_base::sync_with_stdio(false); cin.tie(0)
typedef vector<int> vi;
#define pb push_back
#define REP(i, a, b) for(int i = a; i < b; i++)
#define MAXN 100005
vi adj[MAXN], adj_dfs3[MAXN];
int h[MAXN], crossEdges[MAXN], par[MAXN];
bitset<MAXN> visited;
void dfs(int x) {
visited[x] = true;
for(auto i: adj[x]) if(!visited[i]) {
par[i]=x;
adj_dfs3[x].pb(i);
h[i]=h[x]+1;
dfs(i);
}
}
int dp(int x) {
if(visited[x]) return crossEdges[x];
visited[x] = 1;
//crossEdges[x]=bEdgeU[x]-bEdgeD[x];
for(auto i:adj_dfs3[x]) if(h[i]>h[x]) crossEdges[x]+=dp(i);
return crossEdges[x];
}
int32_t main() {
speed;
int N, E, A, B, ans; cin >> N >> E;
REP(i,0,E) {
cin>>A>>B;
adj[A].pb(B);
adj[B].pb(A);
}
REP(i,1,N+1)if(!visited[i]) dfs(i);
REP(i,1,N+1) visited[i]=0;
REP(i,1,N+1) for(auto j: adj[i]) {
if(h[i]>h[j]) crossEdges[i]++;
else crossEdges[i]--;
}
//REP(i,1,N+1) crossEdges[i]=-1;
REP(i,1,N+1) if(par[i]&&dp(i)==1) cout << i << " " << par[i] << "\n";
}
Compilation message (stderr)
pipes.cpp: In function 'int32_t main()':
pipes.cpp:29:21: warning: unused variable 'ans' [-Wunused-variable]
29 | int N, E, A, B, ans; cin >> N >> E;
| ^~~
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