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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int n,x; cin >> n >> x; 
  6. 	vector<int> arr(n);
  7. 	for(int i = 0; i < n; i++)
  8. 	cin >> arr[i];
  9.  
  10. 	unordered_map<int,int> mp;
  11. 	int cnt = 0;
  12. 	for(int i = 0; i < n; i++){
  13. 		int req = (x - (arr[i]%x))%x;
  14. 		if(mp.find(req) != mp.end())
  15. 		cnt += mp[req];
  16.  
  17. 		mp[arr[i] % x]++;
  18. 	}
  19. 	cout << cnt;
  20. 	return 0;
  21. }
Success #stdin #stdout 0s 5312KB
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stdin
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5 60
31 25 85 29 35
stdout
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3
https://ideone.com/0QZYhX
language:
C++14 (gcc 8.3)
created:
1 hour ago
visibility:
public

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