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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int              long long int
  4. #define double           long double
  5. inline int power(int a, int b) {
  6.     int x = 1;
  7.     while (b) {
  8.         if (b & 1) x *= a;
  9.         a *= a;
  10.         b >>= 1;
  11.     }
  12.     return x;
  13. }
  14.  
  15.  
  16. const int M = 1000000007;
  17. const int N = 3e5+9;
  18. const int INF = 2e9+1;
  19. const int LINF = 2000000000000000001;
  20.  
  21. //_ ***************************** START Below *******************************
  22.  
  23. //* Alternatve way : 
  24. //* freqMap = { 
  25. //*      x -> c1
  26. //* 	 y -> c2
  27. //* 	... -> ...
  28. //* }
  29.  
  30. //* Ans = (1 + 2 + 3 + ... c1-1)   +  (1 + 2+ ... c2-1)   +  ....
  31. //* 	ans = c1(c1-1)/2 + c2(c2-1)/2 
  32.  
  33. //* This is what we do each time with =>  
  34. //* 	ans += mp[val]	
  35. //* 	map[val]++
  36.  
  37.  
  38. vector<int> a;
  39. void consistency(int n) {
  40.  
  41. 	unordered_map<int,int> mp;
  42. 	int ans = 0;
  43.  
  44. 	for(int i=1; i<=n; i++){
  45. 		int val = a[a[a[i]]];
  46. 		if(mp.count(val)){
  47. 			ans += mp[val];
  48. 		}
  49.  
  50. 		mp[val]++;
  51. 	}
  52.  
  53. 	cout << ans << endl;
  54.  
  55. }
  56.  
  57. void solve() {
  58.  
  59.     int n;
  60.     cin >> n;
  61.     a.resize(n+1);
  62.     for(int i=1; i<=n; i++) cin >> a[i];
  63.     consistency(n) ;
  64.  
  65. }
  66.  
  67.  
  68.  
  69.  
  70.  
  71. int32_t main() {
  72.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  73.  
  74.     int t = 1;
  75.     cin >> t;
  76.     while (t--) {
  77.         solve();
  78.     }
  79.  
  80.     return 0;
  81. }
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/0yqQ85
language:
C++14 (gcc 8.3)
created:
9 hours ago
visibility:
public

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