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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. vector<int> a;
  6. int solve(int n, int p, int k){
  7.     unordered_map<int,int> mp;
  8.  
  9.     int ct = 0;
  10.  
  11.     for(int i=0; i<n; i++){
  12.         int val = a[i]%p;
  13.         int power4 = val;
  14.         power4 = (power4 * val)%p;
  15.         power4 = (power4 * val)%p;
  16.         power4 = (power4 * val)%p;
  17.  
  18.         int req = (power4 - (k*val)%p + p)%p;
  19.  
  20.         if(mp.count(req)){
  21.             ct += mp[req];
  22.         }
  23.  
  24.         mp[req]++;
  25.  
  26.     }
  27.  
  28.     return ct;
  29.  
  30. }
  31.  
  32. int main() {
  33.  
  34.     int n, p, k;
  35.     cin >> n >> p >> k;
  36.  
  37.     a.resize(n);
  38.     for(int i=0; i<n; i++) cin >> a[i];
  39.  
  40.     cout << solve(n, p, k) << endl;
  41.  
  42.     return 0;
  43. }
Success #stdin #stdout 0s 5320KB
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https://ideone.com/hYHy4h
language:
C++14 (gcc 8.3)
created:
5 days ago
visibility:
public

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