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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. using ll=long long;
  4.  
  5. int main() {
  6. 	// your code goes here
  7. 	ll n;
  8. 	cin>>n;
  9. 	vector<ll>arr(n+1);
  10. 	for(ll i=1;i<=n;i++) cin>>arr[i];
  11. 	unordered_map<ll,ll>mp;
  12. 	ll ans=0;
  13.  
  14. 	for(ll j=1;j<=n;j++){
  15. 		ans+=mp[arr[arr[arr[j]]]];
  16. 		mp[arr[arr[arr[j]]]]++;
  17.  
  18. 	}
  19. 	cout<<ans<<endl;
  20. 	return 0;
  21. }
Success #stdin #stdout 0s 5324KB
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stdin
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4 
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stdout
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6
https://ideone.com/b5yJmY
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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