API tools faq
paste
Advertisement
tepyotin2

Cycle Finding

tepyotin2
May 21st, 2025
181
0
Never
Add comment
Not a member of Pastebin yet? Sign Up, it unlocks many cool features!
C++ 2.00 KB | None | 0 0
raw download clone embed print report
  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. typedef long long ll;
  6.  
  7. struct Edge{
  8.     int from, to;
  9.     ll weight;
  10. };
  11.  
  12. int t;
  13. int n, m;
  14. vector<Edge> graph;
  15. int parent[5001];
  16. bool visited[5001];
  17.  
  18. void print(int v){
  19.     //cout << "HI" << '\n';
  20.     while(!visited[v]){
  21.         //#1. Find first value to actually begin cycle
  22.         visited[v] = true;
  23.         v = parent[v];
  24.     }
  25.     vector<int> ans;
  26.     int temp = parent[v];
  27.     ans.push_back(v);
  28.     //cout << " v: " << v << '\n';
  29.     //int count = 1;
  30.     while(temp != v){
  31.         //count++;
  32.         //if(count>20) break;
  33.         //cout << "temp: " << temp << '\n';
  34.         ans.push_back(temp);
  35.         temp = parent[temp];
  36.     }
  37.     ans.push_back(v);
  38.     reverse(ans.begin(), ans.end());
  39.     for(auto a: ans){
  40.         cout << " " << a;
  41.     }
  42.     cout << '\n';
  43.     //cout << ans[0] << '\n';
  44. }
  45.  
  46. bool isNegative(){
  47.     vector<ll> dist;
  48.     dist.resize(n+1, 0);
  49.     dist[1] = 0;
  50.     bool check = false;
  51.     for(int i=1; i<=n; i++){
  52.         //cout << "i: " << i << '\n';
  53.         check = false;
  54.         for(Edge e: graph){
  55.             //if(dist[e.from] != INT_MAX){
  56.             //cout << "e.to: " << e.to << ", e.from: " << e.from << ", e.weight: " << e.weight << '\n';
  57.             if(dist[e.to]>dist[e.from]+e.weight){
  58.                 dist[e.to] = dist[e.from]+e.weight;
  59.                 //cout << "i: " << i << ", dist[e.to]: " << dist[e.to] << ", dist[e.from]: " << dist[e.from] << '\n';
  60.                 parent[e.to] = e.from;
  61.                 check = true;
  62.                 if(i==n){
  63.                     cout << "YES";
  64.                     print(e.to);
  65.                     //#1. need to use value that is actually part of cycle or else infinite loop on some cases
  66.                     return true;
  67.                 }
  68.                 //cout << "HI" << '\n';
  69.             }
  70.             //}
  71.         }
  72.         if(!check) break;
  73.     }
  74.     return false;
  75. }
  76.  
  77. int main(){
  78.     //freopen("cyclefind.in", "r", stdin);
  79.    
  80.     cin >> n >> m;
  81.     graph.clear();
  82.     graph.resize(m);
  83.     //dist.resize(n+1, INT_MAX);
  84.     for(int i=0; i<m; i++){
  85.         cin >> graph[i].from >> graph[i].to >> graph[i].weight;
  86.         //cout << graph[i].from << ", " << graph[i].to << ", " << graph[i].weight << '\n';
  87.     }
  88.     if(isNegative()){
  89.         //cout << "YES" << '\n';
  90.     }else{
  91.         cout << "NO" << '\n';
  92.     }
  93.    
  94.     return 0;
  95. }
  96.  
  97.  
Advertisement
Add Comment
Please, Sign In to add comment
Advertisement
Public Pastes
Advertisement
We use cookies for various purposes including analytics. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy.  OK, I Understand
Not a member of Pastebin yet?
Sign Up, it unlocks many cool features!