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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. // Speed
  5. #define fast_io ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
  6.  
  7. // Typedefs
  8. #define int long long
  9. #define pb push_back
  10. #define ff first
  11. #define ss second
  12. #define all(x) (x).begin(), (x).end()
  13. #define rall(x) (x).rbegin(), (x).rend()
  14. #define sz(x) ((int)(x).size())
  15. #define endl '\n'
  16. #define yes cout << "yes\n"
  17. #define no cout << "no\n"
  18.  
  19. // Loops
  20. #define rep(i,a,b) for(int i=a;i<b;++i)
  21. #define per(i,a,b) for(int i=b-1;i>=a;--i)
  22. #define each(x, a) for (auto& x : a)
  23.  
  24. // Consts
  25. const int INF = 1e18;
  26. const int MOD = 1e9+7;
  27. const int N = 2e5 + 5;
  28.  
  29. // Math
  30. int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
  31. int lcm(int a, int b) { return (a / gcd(a, b)) * b; }
  32.  
  33. int power(int a, int b, int m = MOD) {
  34.     int res = 1;
  35.     while (b > 0) {
  36.         if (b & 1) res = res * a % m;
  37.         a = a * a % m;
  38.         b >>= 1;
  39.     }
  40.     return res;
  41. }
  42.  
  43. int modinv(int a, int m = MOD) {
  44.     return power(a, m - 2, m);
  45. }
  46.  
  47. // Logic
  48. void solve() {
  49.     int n;
  50.     cin >> n;
  51.  
  52.     vector<pair<int, int>> a(n);
  53.     rep(i, 0, n) cin >> a[i].ff >> a[i].ss;
  54.  
  55.     vector<int> p(N);
  56.     iota(all(p), 0);
  57.  
  58.     auto find = [&](int x) {
  59.         while (x != p[x]) x = p[x] = p[p[x]];
  60.         return x;
  61.     };
  62.  
  63.     auto unite = [&](int x, int y) {
  64.         x = find(x);
  65.         y = find(y);
  66.         if (x != y) {
  67.             p[y] = x;
  68.             return true;
  69.         }
  70.         return false;
  71.     };
  72.  
  73.     vector<int> s_ind;
  74.     vector<pair<int, int>> si;
  75.  
  76.     rep(i, 0, n) {
  77.         int u = a[i].ff, v = a[i].ss;
  78.         if (unite(u, v)) {
  79.             s_ind.pb(i + 1); 
  80.             si.pb({min(u, v), max(u, v)});
  81.         }
  82.     }
  83.  
  84.     cout << sz(s_ind) << endl;
  85.     each(i, s_ind) cout << i << ' ';
  86.     cout << endl;
  87. }
  88.  
  89. // Main
  90. int32_t main() {
  91.     fast_io;
  92.  
  93.     int t;
  94.     cin >> t;
  95.     while (t--) {
  96.         solve();
  97.     }
  98.  
  99.     return 0;
  100. }
Success #stdin #stdout 0.01s 5308KB
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https://ideone.com/d233ds
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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