#include<iostream>
#include<stack>
#include<map>
#include<vector>
#include<string>
#include<unordered_map>
#include <queue>
#include<cstring>
#include<limits.h>
#include <cassert>
#include<cmath>
#include<set>
#include<algorithm>
#include <iomanip>
#include<numeric> //gcd(a,b)
#include<bitset>
#include <cstdlib>
#include <cstdint>
using namespace std;
#define ll long long
#define f first
//#define endl "\n"
#define s second
#define pii pair<int,int>
#define ppii pair<int,pii>
#define vi vector<int>
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define F(n) for(int i=0;i<n;i++)
#define lb lower_bound
#define ub upper_bound
#define fastio ios::sync_with_stdio(false);cin.tie(NULL);
#pragma GCC optimize ("03,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
using namespace std;
//#define int long long
//#define double long double
const int mxn=1e5,inf=1e9,minf=-1e9;
int lg=0;
vector<vector<int>>up;
vector<vector<int>>adj;
vector<int>h,par;//parent of comp(highest node)
int lca(int a,int b){
if(h[a]<h[b])swap(a,b);
int k=h[a]-h[b];
for(int i=0;i<=lg;i++)if(k&(1<<i))a=up[a][i];
if(a==b)return a;
for(int i=lg;i>=0;i--)if(up[a][i]!=up[b][i])a=up[a][i],b=up[b][i];
return up[a][0];
}
struct dsu{
vector<int>pa;
void init(int n){
pa.assign(n+1,0);
for(int i=1;i<=n;i++)pa[i]=i;
}
int find(int u){return (pa[u]==u)?u:pa[u]=find(pa[u]);}
bool merg(int a,int b,int mode){
a=find(a),b=find(b);
if(a==b)return 0;
pa[a]=b;
if(mode)par[b]=lca(par[b],par[a]);
return 1;
}
}t,t2;
bitset<mxn+10>vis;
vector<vector<pii>>comp;
void bfs(int cur,int p){
queue<pii>q;
q.push({cur,p});
while(!q.empty()){
int cc=q.front().f,cp=q.front().s;
q.pop();
if(vis[cc])continue;
vis[cc]=1;
comp.back().pb({h[cc],cc});
for(auto i:adj[cc]){
if(i==cp)continue;
h[i]=h[cc]+1;
up[i][0]=cc;
q.push({i,cc});
}
}
}
void getans(int cur,int p){
queue<pii>q;
q.push({cur,p});
while(!q.empty()){
int cc=q.front().f,cp=q.front().s;
q.pop();
if(vis[cc])continue;
vis[cc]=1;
for(auto i:adj[cc]){
if(i==cp)continue;
if(t2.find(cc)!=t2.find(i))cout<<cc<<" "<<i<<'\n';
q.push({i,cc});
}
}
}
int32_t main(){
fastio
int n,m;cin>>n>>m;
lg=log2(n)+1;
up.resize(n+2);
for(int i=0;i<=n;i++)up[i].resize(lg+2,0);
adj.resize(n+1);
int a,b;
t.init(n);
t2.init(n);
h.assign(n+1,0);
par.assign(n+1,0);
for(int i=1;i<=n;i++)par[i]=i;
for(int i=0;i<m;i++){
cin>>a>>b;
if(t.merg(a,b,0)){
adj[a].pb(b);
adj[b].pb(a);
}
else t2.merg(a,b,0);
}
vector<int>head;
for(int i=1;i<=n;i++)if(!vis[i]){
comp.pb({});
head.pb(i);
bfs(i,-1);
}
for(auto j:head)for(int i=1;i<=lg;i++)up[j][i]=j;
for(int i=1;i<=lg;i++)for(int j=1;j<=n-1;j++)up[j][i]=up[up[j][i-1]][i-1];
for(int i=1;i<=n;i++){
int x=t2.find(i);
if(par[x])par[x]=lca(par[x],i);
else par[x]=i;
}
for(int i=0;i<comp.size();i++){
sort(rall(comp[i]));
for(auto j:comp[i])if(h[par[t2.find(j.s)]]<h[j.s])t2.merg(j.s,up[j.s][0],1);
}
for(int i=1;i<=n;i++)vis[i]=0;
for(auto j:head)getans(j,-1);
return 0;
}
Compilation message
pipes.cpp: In function 'int32_t main()':
pipes.cpp:135:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<std::pair<int, int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
135 | for(int i=0;i<comp.size();i++){
| ~^~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
1 ms |
348 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
4 ms |
1372 KB |
Output is correct |
2 |
Correct |
4 ms |
1372 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
76 ms |
4068 KB |
Output is correct |
2 |
Correct |
67 ms |
3668 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
126 ms |
7348 KB |
Output is correct |
2 |
Correct |
140 ms |
8160 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
196 ms |
13268 KB |
Output is correct |
2 |
Correct |
166 ms |
13036 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Runtime error |
271 ms |
25208 KB |
Memory limit exceeded |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Runtime error |
453 ms |
33752 KB |
Memory limit exceeded |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Runtime error |
558 ms |
42532 KB |
Memory limit exceeded |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Runtime error |
665 ms |
48324 KB |
Memory limit exceeded |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Runtime error |
828 ms |
54200 KB |
Memory limit exceeded |
2 |
Halted |
0 ms |
0 KB |
- |