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  1. #include <iostream>
  2. #include <iomanip>
  3.  
  4. using namespace std;
  5.  
  6. unsigned long long happy(unsigned int n, unsigned int base)
  7. {
  8.     if (n%2 || n < 2 || base < 2) throw runtime_error("Wrong data");
  9.     auto N = [](unsigned int n, unsigned int k,
  10.                 unsigned int base, auto&&N)
  11.     {
  12.         if (n == 1) return (unsigned long long)(k < base);
  13.         unsigned long long s = 0;
  14.         for(unsigned int l = 0; l < base; ++l) s += N(n-1,k-l,base,N);
  15.         return s;
  16.     };
  17.     unsigned long long s = 0;
  18.     for(unsigned int k = 0; k <= (base-1)*n/2; ++k)
  19.     {
  20.         auto m = N(n/2,k,base,N);
  21.         s += m*m;
  22.     }
  23.     return s;
  24. }
  25.  
  26. int main(int argc, char * argv[])
  27. {
  28.     cout << 13*happy(12,13) << endl;
  29. }
  30.  
Success #stdin #stdout 0.05s 5620KB
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9203637295151
https://ideone.com/bKXCqb
language:
C++14 (gcc 8.3)
created:
2 years ago
visibility:
public

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