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  1. #include <stdio.h>
  2.  
  3. #define N 200005
  4.  
  5. int c[N], size[N];
  6.  
  7. int find(int x) {
  8.     if (x != c[x])
  9.         c[x] = find(c[x]);
  10.     return c[x];
  11. }
  12.  
  13. int unite(int x, int y) {
  14.     x = find(x);
  15.     y = find(y);
  16.     if (x == y) return 0;
  17.     if (size[x] < size[y]) {
  18.         int temp = x;
  19.         x = y;
  20.         y = temp;
  21.     }
  22.     c[y] = x;
  23.     size[x] += size[y];
  24.     return 1;
  25. }
  26.  
  27. void solve() {
  28.     int n;
  29.     scanf("%d", &n);
  30.  
  31.     for (int i = 0; i < N; ++i) {
  32.         c[i] = i;
  33.         size[i] = 1;
  34.     }
  35.  
  36.     int s_indices[N], s_count = 0;
  37.  
  38.     for (int i = 0; i < n; ++i) {
  39.         int u, v;
  40.         scanf("%d %d", &u, &v);
  41.         if (unite(u, v)) {
  42.             s_indices[s_count++] = i + 1;
  43.         }
  44.     }
  45.  
  46.     printf("%d\n", s_count);
  47.     for (int i = 0; i < s_count; ++i)
  48.         printf("%d ", s_indices[i]);
  49.     printf("\n");
  50. }
  51.  
  52. int main() {
  53.     int t;
  54.     scanf("%d", &t);
  55.     while (t--) {
  56.         solve();
  57.     }
  58.     return 0;
  59. }
  60.  
Success #stdin #stdout 0.01s 5280KB
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https://ideone.com/tCX6zN
language:
C (gcc 8.3)
created:
2 days ago
visibility:
public

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