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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. #define MAX 1000
  5.  
  6. typedef struct Node {
  7.     int v;
  8.     struct Node* next;
  9. } Node;
  10.  
  11. Node* adj[MAX];
  12. int visited[MAX], recStack[MAX];
  13. int n;
  14.  
  15. void addEdge(int u, int v) {
  16.     Node* temp = (Node*)malloc(sizeof(Node));
  17.     temp->v = v;
  18.     temp->next = adj[u];
  19.     adj[u] = temp;
  20. }
  21.  
  22. int dfs(int v) {
  23.     visited[v] = 1;
  24.     recStack[v] = 1;
  25.  
  26.     for (Node* temp = adj[v]; temp != NULL; temp = temp->next) {
  27.         int u = temp->v;
  28.  
  29.         if (!visited[u] && dfs(u))
  30.             return 1;
  31.         else if (recStack[u])
  32.             return 1;
  33.     }
  34.  
  35.     recStack[v] = 0;
  36.     return 0;
  37. }
  38.  
  39. int main() {
  40.     int m, u, v;
  41.     scanf("%d %d", &n, &m);
  42.  
  43.     for (int i = 0; i < n; i++) adj[i] = NULL;
  44.  
  45.     for (int i = 0; i < m; i++) {
  46.         scanf("%d %d", &u, &v);
  47.         if (u >= 0 && u < n && v >= 0 && v < n)
  48.             addEdge(u, v);
  49.     }
  50.  
  51.     for (int i = 0; i < n; i++) {
  52.         if (!visited[i] && dfs(i)) {
  53.             printf("YES\n");
  54.             return 0;
  55.         }
  56.     }
  57.  
  58.     printf("NO\n");
  59.     return 0;
  60. }
Success #stdin #stdout 0s 5328KB
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stdout
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YES
https://ideone.com/adJ77f
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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