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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. /* Guss-Jordan */
  5. #define N 3
  6. int main() {
  7.   int i, j, k, x, y;
  8.   double r, max;
  9.   double a[N][N + 1] = {
  10.     { 2.0,  3.0,  1.0,  4.0 },
  11.     { 4.0,  1.0, -3.0, -2.0 }, 
  12.     {-1.0,  2.0,  2.0,  2.0 } };
  13.  
  14.   /* forward */
  15.   for (i = 0; i < N; i++) {
  16.     /* pivotting */
  17.     max = fabs(a[i][i]);
  18.     k = i;
  19.     for (j = i + 1; j < N; j++)
  20.       if (max < fabs(a[j][i])) {
  21.         max = fabs(a[j][i]);
  22.         k = j;
  23.       }
  24.     if (k != i)
  25.       for (j = 0; j <= N; j++) {
  26.         r = a[k][j];
  27.         a[k][j] = a[i][j];
  28.         a[i][j] = r;
  29.       }
  30.     /* pivotting finished */
  31.  
  32.     r = a[i][i];
  33.     for (j = i ; j <= N; j++)
  34.       a[i][j] /= r;
  35.  
  36.     for (j = i + 1; j < N; j++) {
  37.       r = a[j][i];
  38.       for (k = 0; k <= N; k++) {
  39.         a[j][k] /= r;
  40.         a[j][k] -= a[i][k];
  41.       }
  42.     }
  43.   }
  44.  
  45.   /* backward */
  46.   for (i = N - 1; i >= 0; i--) {
  47.     for (j = i - 1; j >= 0; j--) {
  48.       a[j][N] -= a[i][N] * a[j][i];
  49.       a[j][i] = 0.0;
  50.     }
  51.   }
  52.   for (y = 0; y < N; y++) {
  53.     for (x = 0; x <= N; x++)
  54.       printf("%+.2f ", a[y][x]);
  55.     putchar('\n');
  56.   }
  57.   putchar('\n');
  58.   return 0;
  59. }
  60. /* end */
  61.  
Success #stdin #stdout 0.02s 1720KB
comments (?)
stdin
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Standard input is empty
stdout
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+1.00 +0.00 +0.00 +2.00 
+0.00 +1.00 +0.00 -1.00 
+0.00 +0.00 +1.00 +3.00
https://ideone.com/QukPdf
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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