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  1.  
  2.     #include <vector>
  3.     #include <iostream>
  4.  
  5.     std::vector<unsigned int> pascal(unsigned int n)
  6.     {
  7.         // This variable is static, to cache results.
  8.         // Not a problem, as long as mathematics do not change between two calls,
  9.         // which is unlikely to happen, hopefully.
  10.         static std::vector<std::vector<unsigned int> > triangle;
  11.  
  12.         if(triangle.size() <= n)
  13.         {
  14.             // Compute for i = last to n-1
  15.             while(triangle.size() != n)
  16.                 pascal(triangle.size());
  17.  
  18.             // Compute for n
  19.             if(n == 0)
  20.                 triangle.push_back(std::vector<unsigned int>(1,1));
  21.             else
  22.             {
  23.                 std::vector<unsigned int> result(n + 1, 0);
  24.                 for(unsigned int k = 0; k <= n; k++)
  25.                 {
  26.                     unsigned int l = (k > 0 ? triangle[n - 1][k - 1] : 0);
  27.                     unsigned int r = (k < n ? triangle[n - 1][k] : 0);
  28.                     result[k] = l + r;
  29.                 }
  30.                 triangle.push_back(result);
  31.             }
  32.         }
  33.  
  34.         // Finish
  35.         return triangle[n];
  36.     }
  37.  
  38.     std::ostream& operator<<(std::ostream& out, const std::vector<unsigned int>& v)
  39.     {
  40.         for(unsigned int t = 0; t < v.size(); t++)
  41.             out << v[t] << " ";
  42.         return out;
  43.     }
  44.  
  45.     int main()
  46.     {
  47.         for(unsigned int t = 0; t < 6; t++)
  48.             std::cout << pascal(t) << "\n";
  49.     }
  50.  
  51.  
Success #stdin #stdout 0.02s 2860KB
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1 2 1 
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1 4 6 4 1 
1 5 10 10 5 1
https://ideone.com/oE1yR1
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

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