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  1. #include <stdio.h>
  2.  
  3. #define N 2
  4.  
  5. void solveLinearEquations(double a[N][N+1]) {
  6.     double x[N];
  7.     int i, j, k;
  8.  
  9.     // ガウス消去法で方程式を解く
  10.     for (i = 0; i < N; i++) {
  11.         // ピボット選択と正規化
  12.         for (k = i + 1; k < N; k++) {
  13.             double factor = a[k][i] / a[i][i];
  14.             for (j = i; j <= N; j++) {
  15.                 a[k][j] -= factor * a[i][j];
  16.             }
  17.         }
  18.     }
  19.  
  20.     // 後退代入法で解を計算
  21.     for (i = N - 1; i >= 0; i--) {
  22.         x[i] = a[i][N];
  23.         for (j = i + 1; j < N; j++) {
  24.             x[i] -= a[i][j] * x[j];
  25.         }
  26.         x[i] /= a[i][i];
  27.     }
  28.  
  29.     // 結果の出力
  30.     for (i = 0; i < N; i++) {
  31.         printf("x[%d] = %.2f\n", i + 1, x[i]);
  32.     }
  33. }
  34.  
  35. int main(void) {
  36.     // 連立方程式の係数行列
  37.     double a[N][N + 1] = {
  38.         {1.0, 1.0, 8.0},   // x + y = 8
  39.         {230.0, 310.0, 2080.0} // 230x + 310y = 2080
  40.     };
  41.  
  42.     // 解の計算
  43.     solveLinearEquations(a);
  44.  
  45.     return 0;
  46. }
  47.  
Success #stdin #stdout 0.01s 5268KB
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stdin
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Standard input is empty
stdout
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x[1] = 5.00
x[2] = 3.00
https://ideone.com/T1ElYI
language:
C (gcc 8.3)
created:
4 days ago
visibility:
public

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