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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int n;
  6. 	cin>>n;
  7.  
  8. 	vector<int> numbers(n);
  9.  
  10. 	for(int i=0; i<n; i++){
  11. 		cin>>numbers[i];
  12. 	}
  13.  
  14. 	int answer = 0;
  15.  
  16. 	unordered_map<int,int> modFreq;
  17.  
  18. 	for(int i=0; i<n; i++){
  19. 		if(modFreq.find((5 - numbers[i]%5)%5) != modFreq.end()){
  20. 			answer += modFreq[(5 - numbers[i]%5)%5];
  21. 		}
  22.  
  23. 		modFreq[numbers[i]%5]++;
  24. 	}
  25.  
  26. 	cout<<answer;
  27.  
  28. 	return 0;
  29. }
Success #stdin #stdout 0.01s 5280KB
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stdin
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6
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stdout
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5
https://ideone.com/u9OiUG
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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