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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. using namespace std;
  5.  
  6. void lu_decomposition(const std::vector<std::vector<double> > &vals)
  7. {
  8.  
  9.     int i = 0, j = 0, k = 0;
  10.     for (i = 0; i < n; i++)
  11.     {
  12.         for (j = 0; j < n; j++)
  13.         {
  14.             if (j < i)
  15.                 l[j][i] = 0;
  16.             else
  17.             {
  18.                 l[j][i] = vals[j][i];
  19.                 for (k = 0; k < i; k++)
  20.                 {
  21.                     l[j][i] = l[j][i] - l[j][k] * u[k][i];
  22.                 }
  23.             }
  24.         }
  25.         for (j = 0; j < n; j++)
  26.         {
  27.             if (j < i)
  28.                 u[i][j] = 0;
  29.             else if (j == i)
  30.                 u[i][j] = 1;
  31.             else
  32.             {
  33.                 u[i][j] = vals[i][j] / l[i][i];
  34.                 for (k = 0; k < i; k++)
  35.                 {
  36.                     u[i][j] = u[i][j] - ((l[i][k] * u[k][j]) / l[i][i]);
  37.                 }
  38.             }
  39.         }
  40.     }
  41. }
  42.  
  43. int main() {
  44. 	// your code goes here
  45.  
  46. 	std::vector<std::vector<double> > data = {
  47.  
  48. 		{5, 2, 1, 12, 8},
  49.     	{1, 4, 3, 4, 5},
  50.     	{7, 4, 1, 7, 2},
  51.     	{7, 8, 6, 4, 1},
  52.     	{8, 1, 2, 3, 5},
  53. 	};
  54. 	std::vector<std::vector<double> > l(5, std::vector<double>(5)); 
  55. 	std::vector<std::vector<double> > u(5, std::vector<double>(5));
  56.  
  57. 	int n = 5; 
  58.  
  59. 	lu_decomposition(data, l, u);
  60.  
  61.  
  62.     std::cout << "U" << std::endl;
  63.     for(unsigned i = 0; (i < n); i++)
  64.     {
  65.     	for(unsigned j=0; (j < n); j++)
  66.     	{
  67.     		std::cout << u[i][j] << ' ';
  68.     	}	
  69.     	std::cout << std::endl;
  70.     }
  71.     std::cout << std::endl;
  72.     std::cout << "L" << std::endl;
  73.       for(unsigned i = 0; (i < n); i++)
  74.     {
  75.     	for(unsigned j=0; (j < n); j++)
  76.     	{
  77.     		std::cout << l[i][j] << ' ';
  78.     	}	
  79.     	std::cout << std::endl;
  80.     }
  81. }
  82.  
  83.  
Success #stdin #stdout 0s 3276KB
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stdin
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Standard input is empty
stdout
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U
1 0.4 0.2 2.4 1.6 
0 1 0.777778 0.444444 0.944444 
0 0 1 7.75 7.75 
0 0 0 1 1 
0 0 0 0 1 

L
5 0 0 0 0 
1 3.6 0 0 0 
7 1.2 -1.33333 0 0 
7 5.2 0.555556 -19.4167 0 
8 -2.2 2.11111 -31.5833 9.5
https://ideone.com/XSFdMQ
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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