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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.     int max_val = 0;
  54.  
  55.     rep(i, 0, n) {
  56.         cin >> a[i].ff >> a[i].ss;
  57.         max_val = max({max_val, a[i].ff, a[i].ss});
  58.     }
  59.  
  60.     vector<int> p(max_val + 5);
  61.     iota(all(p), 0);
  62.  
  63.     auto find = [&](int x) {
  64.         while (x != p[x]) x = p[x] = p[p[x]];
  65.         return x;
  66.     };
  67.  
  68.     auto unite = [&](int x, int y) {
  69.         x = find(x);
  70.         y = find(y);
  71.         if (x != y) {
  72.             p[y] = x;
  73.             return true;
  74.         }
  75.         return false;
  76.     };
  77.  
  78.     vector<int> s_ind;
  79.     vector<pair<int, int>> si;
  80.  
  81.     rep(i, 0, n) {
  82.         int u = a[i].ff, v = a[i].ss;
  83.         if (unite(u, v)) {
  84.             s_ind.pb(i + 1); 
  85.             si.pb({min(u, v), max(u, v)});
  86.         }
  87.     }
  88.  
  89.     cout << sz(s_ind) << endl;
  90.     each(i, s_ind) cout << i << ' ';
  91.     cout << endl;
  92. }
  93.  
  94. // Main
  95. int32_t main() {
  96.     fast_io;
  97.  
  98.     int t;
  99.     cin >> t;
  100.     while (t--) {
  101.         solve();
  102.     }
  103.  
  104.     return 0;
  105. }
  106.  
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/mCbeY3
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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