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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     int n; cin>>n;
  6.      int d ; cin>>d;
  7.      int a[n];
  8.       for(int i=0;i<n;i++) {cin>> a[i]; a[i]%=d;}
  9.  
  10.       unordered_map<int,int> mp;
  11.       int ans=0;
  12.        for(int k=0;k<n;k++){
  13.             ans+=mp[(d-a[k])%d];
  14.             for(int i=0;i<k;i++){
  15.                 mp[(a[i]+a[k])%d]++;
  16.             }
  17.        }
  18.         cout<<ans;
  19.  
  20. }
  21.  
Success #stdin #stdout 0s 5300KB
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stdin
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5 5
3 3 4 7 8
stdout
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3
https://ideone.com/xXieMk
8
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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