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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define ll long long
  4. #define pb push_back
  5. #define fi first
  6. #define se second
  7. #define all(x) x.begin(),x.end()
  8. const ll MAXN=1e6+5,MOD=998244353,INF=1e9,LG=16,MAX=2e6;
  9. ll i,n,m,j,k,p,t,ans,nex[MAXN],pre[MAXN],b[MAXN];
  10. struct h{
  11.     ll pre,suf;
  12. } a[MAXN];
  13. int main(){
  14.     ios::sync_with_stdio(0);
  15.     cin.tie(0);cout.tie(0);
  16.     // freopen("changedir.inp","r",stdin);
  17.     // freopen("changedir.out","w",stdout);
  18.     cin>>n;
  19.     for(i=1;i<=n;i++){
  20.         cin>>a[i].pre>>a[i].suf;
  21.         nex[a[i].pre]=a[i].suf;
  22.         pre[a[i].suf]=a[i].pre;
  23.     }
  24.     ll cur=nex[0],id=2;
  25.     while(cur!=0){
  26.         b[id]=cur;
  27.         ll luu=cur;
  28.         cur=nex[cur];
  29.         nex[luu]=0;
  30.         pre[luu]=0;
  31.         id+=2;
  32.     }
  33.     for(i=1;i<=MAX;i++){
  34.         if(nex[i]&&!pre[i]){
  35.             cur=i;
  36.             break;
  37.         }
  38.     }
  39.     id=1;
  40.     while(cur!=0){
  41.         b[id]=cur;
  42.         ll luu=cur;
  43.         cur=nex[cur];
  44.         nex[luu]=0;
  45.         pre[luu]=0;
  46.         id+=2;
  47.     }
  48.     for(i=1;i<=n;i++)
  49.         cout<<b[i]<<" ";
  50. }
Success #stdin #stdout 0.01s 7596KB
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https://ideone.com/6t4EXg
language:
C++14 (gcc 8.3)
created:
22 hours ago
visibility:
public

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