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  1. /*
  2. Name: Md. Shahin Shiddik Shuvon
  3. Id: 230241011
  4. Report: Cramer's rule
  5. */
  6. #include <bits/stdc++.h>
  7. using namespace std;
  8.  
  9.  
  10. // 3x3 determinant
  11. float det3x3(float m[3][3]) {
  12.     return m[0][0]*(m[1][1]*m[2][2] - m[1][2]*m[2][1])
  13.          - m[0][1]*(m[1][0]*m[2][2] - m[1][2]*m[2][0])
  14.          + m[0][2]*(m[1][0]*m[2][1] - m[1][1]*m[2][0]);
  15. }
  16.  
  17. int main() {
  18.     int n;
  19.     cin >> n;
  20.  
  21.  
  22.  
  23.     float A[3][3] = {0}, B[3] = {0}; // initialized to 0
  24.  
  25.     cout << "Enter coefficients of matrix A:\n";
  26.     for (int i = 0; i < n; i++)
  27.         for (int j = 0; j < n; j++)
  28.             cin >> A[i][j];
  29.  
  30.     cout << "Enter constants of vector B:\n";
  31.     for (int i = 0; i < n; i++)
  32.         cin >> B[i];
  33.  
  34.  
  35.         float detA = det3x3(A);
  36.         cout << "\nDeterminant of A: " << detA << endl;
  37.         if (detA == 0) {
  38.             cout << "Matrix is singular; not uniquely solvable.\n";
  39.             return 0;
  40.         }
  41.  
  42.         float A1[3][3], A2[3][3], A3[3][3];
  43.         for (int i = 0; i < 3; i++) {
  44.             A1[i][0] = B[i]; A1[i][1] = A[i][1]; A1[i][2] = A[i][2];
  45.             A2[i][0] = A[i][0]; A2[i][1] = B[i]; A2[i][2] = A[i][2];
  46.             A3[i][0] = A[i][0]; A3[i][1] = A[i][1]; A3[i][2] = B[i];
  47.         }
  48.  
  49.         float x1 = det3x3(A1) / detA;
  50.         float x2 = det3x3(A2) / detA;
  51.         float x3 = det3x3(A3) / detA;
  52.  
  53.         cout << "\nThe solution using Cramer's Rule:\n";
  54.         cout << "x1 = " << x1 << endl;
  55.         cout << "x2 = " << x2 << endl;
  56.         cout << "x3 = " << x3 << endl;
  57.  
  58.  
  59.     return 0;
  60. }
Success #stdin #stdout 0s 5320KB
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stdin
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3
1 1 1
2 3 5
4 0 5

5 8 2
stdout
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Enter coefficients of matrix A:
Enter constants of vector B:

Determinant of A: 13

The solution using Cramer's Rule:
x1 = 3
x2 = 4
x3 = -2
https://ideone.com/d52fXc
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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