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  1. #include <stdlib.h>
  2. #include <stdio.h>
  3. #include <math.h>
  4.  
  5. void print(double ** m, int N)
  6. {
  7.     for(int i = 0; i < N; ++i)
  8.     {
  9.         for(int j = 0; j < N; ++j)
  10.         {
  11.             printf("%.1lf ",m[i][j]);
  12.         }
  13.         puts("");
  14.     }
  15.     puts("");
  16. }
  17.  
  18.  
  19. double GaussDet(double**m, int n)
  20. {
  21.     double det = 1;
  22.     for(int i = 0; i < n; ++i)
  23.     {
  24.         double mx = fabs(m[i][i]);
  25.         int idx = i;
  26.         for(int j = i+1; j < n; ++j)
  27.             if (mx < fabs(m[i][j])) mx = fabs(m[i][idx = j]);
  28.         if (idx != i)
  29.         {
  30.             for(int j = i; j < n; ++j)
  31.             {
  32.                 double t = m[j][i];
  33.                 m[j][i] = m[j][idx];
  34.                 m[j][idx] = t;
  35.             }
  36.             det = -det;
  37.         }
  38.         for(int k = i+1; k < n; ++k)
  39.         {
  40.             double t = m[k][i]/m[i][i];
  41.  
  42.             for(int j = i; j < n; ++j)
  43.                 m[k][j] -= m[i][j]*t;
  44.         }
  45.     }
  46.     for(int i = 0; i < n; ++i) det *= m[i][i];
  47.     return det;
  48. }
  49.  
  50.  
  51. int main(int argc, const char * argv[])
  52. {
  53.     #define  N  5
  54.     double ** m = malloc(N*sizeof(double*));
  55.     for(int i = 0; i < N; ++i) m[i] = malloc(N*sizeof(double));
  56.  
  57.     for(int i = 0; i < N; ++i)
  58.     {
  59.         for(int j = 0; j < N; ++j)
  60.         {
  61.             m[i][j] = rand()%10;
  62.         }
  63.     }
  64.     m[0][0] = 0;
  65.     print(m,N);
  66.  
  67.     printf("Det = %lf\n",GaussDet(m,N));
  68.  
  69. }
  70.  
Success #stdin #stdout 0s 5280KB
comments (?)
stdin
copy 
1 2 3 
4 5 6 
7 8 9
stdout
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0.0 6.0 7.0 5.0 3.0 
5.0 6.0 2.0 9.0 1.0 
2.0 7.0 0.0 9.0 3.0 
6.0 0.0 6.0 2.0 6.0 
1.0 8.0 7.0 9.0 2.0 

Det = -2062.000000
https://ideone.com/dLCIWR
language:
C (gcc 8.3)
created:
3 days ago
visibility:
public

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