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  1. #include <iostream>
  2. #include <iomanip>
  3. #include <cmath>
  4. using namespace std;
  5.  
  6. int main() {
  7.     int n;
  8.     cout << "Enter the order of square matrix: ";
  9.     cin >> n;
  10.  
  11.     double a[n][n + 1], x[n];
  12.  
  13.     cout << "Enter the elements of augmented matrix row-wise:\n";
  14.     for (int i = 0; i < n; i++) {
  15.         for (int j = 0; j <= n; j++) {
  16.             cin >> a[i][j];
  17.         }
  18.     }
  19.  
  20.     // Forward Elimination to get upper triangular matrix
  21.     for (int i = 0; i < n; i++) {
  22.         // Partial pivoting (optional but improves accuracy)
  23.         for (int k = i + 1; k < n; k++) {
  24.             if (fabs(a[i][i]) < fabs(a[k][i])) {
  25.                 for (int j = 0; j <= n; j++) {
  26.                     swap(a[i][j], a[k][j]);
  27.                 }
  28.             }
  29.         }
  30.  
  31.         for (int k = i + 1; k < n; k++) {
  32.             double factor = a[k][i] / a[i][i];
  33.             for (int j = 0; j <= n; j++) {
  34.                 a[k][j] -= factor * a[i][j];
  35.             }
  36.         }
  37.     }
  38.  
  39.     // Backward Substitution
  40.     for (int i = n - 1; i >= 0; i--) {
  41.         x[i] = a[i][n];
  42.         for (int j = i + 1; j < n; j++) {
  43.             x[i] -= a[i][j] * x[j];
  44.         }
  45.         x[i] /= a[i][i];
  46.     }
  47.  
  48.     // Output the solution
  49.     cout << "\nThe solution is:\n";
  50.     for (int i = 0; i < n; i++) {
  51.         cout << "x" << i + 1 << " = " << fixed << setprecision(6) << x[i] << endl;
  52.     }
  53.  
  54.     return 0;
  55. }
  56.  
Success #stdin #stdout 0.01s 5292KB
comments (?)
stdin
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3 6 -9 15
2 4 -6 10
-2 -3 4 -6
stdout
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Enter the order of square matrix: Enter the elements of augmented matrix row-wise:

The solution is:
x1 = -nan
x2 = -inf
x3 = -inf
https://ideone.com/teDp39
language:
C++14 (gcc 8.3)
created:
13 days ago
visibility:
public

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