fork download
copy 
  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. 	for(int i=1; i<=n; i++){
  44. 		if(mp.count(a[a[a[i]]])){
  45. 			ans += mp[a[a[a[i]]]];
  46. 		}
  47. 		mp[a[a[a[i]]]]++;
  48. 	}
  49.  
  50.  
  51. 	cout << ans << endl;
  52.  
  53. }
  54.  
  55. void solve() {
  56.  
  57.     int n;
  58.     cin >> n;
  59.     a.resize(n+1);
  60.     for(int i=1; i<=n; i++) cin >> a[i];
  61.     consistency(n) ;
  62.  
  63. }
  64.  
  65.  
  66.  
  67.  
  68.  
  69. int32_t main() {
  70.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  71.  
  72.     int t = 1;
  73.     cin >> t;
  74.     while (t--) {
  75.         solve();
  76.     }
  77.  
  78.     return 0;
  79. }
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
copy 
1
4
4 2 1 2
stdout
copy 
6
https://ideone.com/ZaY0ae
language:
C++14 (gcc 8.3)
created:
8 hours ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!