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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4. #include <iterator>
  5. #include <string>
  6. #include<bits/stdc++.h>
  7. #include<queue>
  8. #include<deque>
  9. #include<stack>
  10. #include<set>
  11. using namespace std;
  12. void fast()
  13. {
  14.     ios::sync_with_stdio(false);
  15.     cin.tie(nullptr);
  16.     cout.tie(nullptr);
  17.  
  18.  
  19. }
  20.  
  21. void george_dictator_2()
  22. {
  23.     int n,k;
  24.     cin>>n>>k;
  25.     vector<int>v(n);
  26.     vector<int>freq(2000001,0),freq_ne(2000001,0);
  27.     for(int i=0; i<n; i++)
  28.     {
  29.         cin>>v[i];
  30.         if(v[i]<0)
  31.         {
  32.             freq_ne[v[i]*-1]++;
  33.         }
  34.         else
  35.         {
  36.             freq[v[i]]++;
  37.         }
  38.     }
  39.     sort(v.begin(),v.end());
  40.     long long cont=0;
  41.  
  42.  
  43.         for(int i=0; i<n; i++)
  44.     {
  45.        int  x=k-v[i];
  46.  
  47.         if(x<0)
  48.         {
  49.           if(x==v[i])
  50.           {
  51.               cont+=freq_ne[x*-1]-1;
  52.           }
  53.  
  54.             else{
  55.                     cont+=freq_ne[x*-1];
  56.             }
  57.         }
  58.         else
  59.         {
  60.             if(x==v[i])
  61.             {
  62.                 cont+=freq[x]-1;
  63.             }
  64.             else
  65.             {
  66.                 cont+=freq[x];
  67.             }
  68.         }
  69.         if(v[i]<0)
  70.         {
  71.             if(freq_ne[v[i]*-1]>0)
  72.             {
  73.                 freq_ne[v[i]*-1]--;
  74.  
  75.             }
  76.  
  77.         }
  78.         else
  79.         {
  80.             if(freq[v[i]]>0)
  81.             {
  82.                 freq[v[i]]--;
  83.             }
  84.         }
  85.  
  86.     }
  87.  
  88.     cout<<cont;
  89.  
  90. }
  91.  
  92.  
  93. int main()
  94. {
  95.     fast();
  96.  
  97.  
  98.     george_dictator_2();
  99.  
  100.  
  101.     return 0;
  102. }
  103.  
Success #stdin #stdout 0.01s 18888KB
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https://ideone.com/TYFseF
language:
C++ (gcc 8.3)
created:
6 hours ago
visibility:
public

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