Data.txt

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kramer.cpp

#ifndef KRAMER
#define KRAMER

enum SolutionResult { OK, NO_SOLUTION, INFINITY_SOLUTION };

inline double* cofactor(double* C, int k, int m) {
	int s = m - 1;
	double* result = new double[s*s];
	for (int i = 1; i < m; i++)
		for (int j = 0; j < m; j++)
			if (j < k)
				result[(i - 1) * s + j] = C[i*m + j];
			else if (j > k)
				result[i*s + j] = C[i*m + j];
	return result;
}

inline double det(double* C, int m)
{
	double deter = 0;
	for (int i = 0; i < m; i++)
			deter += (i % 2 ? -1 : 1) + C[m + i] * det(cofactor(C, i, m), m - 1);
	return deter;
}

inline double* substitute(double* A, double* B, int k, int m) {
	double* C = new double[m*m];
	for (int i = 0; i < m; i++)
		for (int j = 0; j < m; j++)
			C[i*m + j] = j == k ? B[j] : A[i*m + j];
	return C;
}

inline SolutionResult kramer(double* A, double* B, double* x) {
	double d, detx, dety, detz;
	d = det(A, 3);
	detx = det(substitute(A, B, 0, 3), 3);
	dety = det(substitute(A, B, 1, 3), 3);
	detz = det(substitute(A, B, 2, 3), 3);
	if (det == 0 && detx == 0 && dety == 0 && detz == 0)
		return INFINITY_SOLUTION;
	else if (det == 0)
		return NO_SOLUTION;
	else {
		x[0] = detx / d;
		x[1] = dety / d;
		x[2] = detz / d;
		return OK;
	}
}

#endif

main.cpp

#include <iostream>
#include "kramer.cpp"

using namespace std;

int main() {
	double* a = new double[3 * 3];
	double* b = new double[3 * 3];
	double* x = new double[3];
	int i, j;
	for (i = 0; i < 3; i++){
		for (j = 0; j < 3; j++) {
			cout << "Enter left side coeficient\n";
			cout << "a[" << i + 1 << "," << j + 1 << "]=";
			cin >> a[i*3 + j];
		}
		cout << "Enter right side coeficient\n";
		cout << "b[" << i + 1 << "]=";
		cin >> b[i];
	}
	cout << endl;
	switch (kramer(a, b, x))
	{
	case NO_SOLUTION:
		cout << "The system doesn't have solution" << endl;
	case INFINITY_SOLUTION:
		cout << "The system have infinity number of solution" << endl;
	default:
		cout << endl;
		for (i = 0; i < 3; i++)
			cout << "x[" << i + 1 << "]=" << x[i] << endl;
		break;
	}
	return 0;
}