practice

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <iomanip>
#include <string.h>
using namespace  std;
float** matrix = new float* [4];
float* answers = new float[3];
void printmatrix(float** matrix)
{
	cout.setf(ios::fixed, ios::floatfield);
	cout.setf(ios::showpoint);

	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 5; j++)
		{

			cout.width(10);
			cout.precision(5);
			if (j != 4)
				cout << matrix[i][j] << setprecision(5) << "*x" << j + 1 << " + ";
			else
			{
				cout.width(2);
				cout.precision(5);
				cout << "=" << matrix[i][j];
			}
		}
		cout << endl;
	}
}//печать матрицы
FILE* fromfile(FILE* file, float** matrix)
{
	int countrow = 0;
	int countcoll = 0;
	char* string = new char[30];
	while (fgets(string, 128, file) > 0)
	{
		if (strlen(string) < 12)
			continue;
		char* pch = strtok(string, " \n");
		while (pch != NULL)                         // пока есть лексемы
		{
			matrix[countrow][countcoll] = atof(pch);
			pch = strtok(NULL, " \n");
			countcoll++;
		}
		countrow++;
		countcoll = 0;
	}
	fclose(file);
	return(file);
}//запись из файла в матрицу
void matrixgen(float** matrix)// создание матрицы
{
	for (int i = 0; i < 4; i++)
	{
		matrix[i] = new float[5]; // Создаем элементы
	}
}
float swap(float** matrix, int n, int k)//n меняем с k
{
	float buffer;
	for (int j = 0; j < 5; j++)
	{
		buffer = matrix[n][j];
		matrix[n][j] = matrix[k][j];
		matrix[k][j] = buffer;
	}
	return(**matrix);
}
void solution(float** matirx, float* answers)
{
	answers[3] = matrix[3][4] / matrix[3][3];
	answers[2] = (matrix[2][4] - answers[3] * matrix[2][3]) / matrix[2][2];
	answers[1] = (matrix[1][4] - answers[2] * matrix[1][2] - answers[3] * matrix[1][3]) / matrix[1][1];
	answers[0] = (matrix[0][4] - answers[1] * matrix[0][1] - answers[2] * matrix[0][2] - answers[3] * matrix[0][3]) / matrix[0][0];
	for (int i = 1; i < 5; i++)
		cout << "x" << i << "=" << answers[i - 1] << endl;
}
void gauss_straight(float** matrix)
{
	int zerorow = -1;
	float buff;
	for (int row = 0; row < 4; row++)
	{
		if (matrix[row][row] == 0)//если главный элемент равен 0, то нужно найти другую строку и поменять их местами
		{
			for (int i = row; i < 4; i++)
				if (matrix[i][row] != 0)
					zerorow = i;
			if (zerorow == -1) { cout << "SLAU doesn't have solutions/infinite solutions"; return; }
			swap(matrix, row, zerorow);
			zerorow = -1;
		}
		for (int extrarow = row + 1; extrarow < 4; extrarow++)
		{
			buff = -matrix[extrarow][row];
			for (int col = 0; col < 6; col++)
			{

				matrix[extrarow][col] += matrix[row][col] * buff / matrix[row][row];
			}
		}
	}
	puts("Row echelon form");
	printmatrix(matrix);
	solution(matrix, answers);
}

void gauss_partly(float** matrix)
{
	float max = 0;
	int zerorow = -1;
	float buff;
	for (int row = 0; row < 4; row++)
	{
		for (int i = row; i < 4; i++)
			if (fabs(matrix[i][row]) > max)
			{
				zerorow = i;
				max = fabs(matrix[i][row]);
			}
		if (max == 0) { cout << "SLAU doesn't have solutions/infinite solutions"; return; }
		swap(matrix, row, zerorow);
		max = 0;
		zerorow = -1;
		for (int extrarow = row + 1; extrarow < 4; extrarow++)
		{
			buff = -matrix[extrarow][row];
			for (int col = 0; col < 6; col++)
			{

				matrix[extrarow][col] += matrix[row][col] * buff / matrix[row][row];
			}
		}
	}
	puts("Row echelon form");
	printmatrix(matrix);
	solution(matrix, answers);
}
int main()
{
	matrixgen(matrix);
	double precisematrix[4][5];
	FILE* file;
	char* name;
	name = new char[15];
	puts("input file name");
	cin >> name;
	fopen_s(&file, name, "r");
	if (file == NULL)
	{
		puts("file not found");
		return(0);
	}
	fromfile(file, matrix);
	cout << "file read successfully" << endl;
	printmatrix(matrix);
	cout << "gauss straight" << endl;
	//gauss_straight(matrix);
	gauss_partly(matrix);
}