Умножение-сумма матриц

#include "pch.h"
#include <iostream>
#include <fstream>
#include<iomanip>
using namespace std;

int**create(ifstream &f, int n, int m)
{
	int i, j;

	int**a = new int *[n];
	for (i = 0; i < m; i++)
		a[i] = new int[n];
	for (i = 0; i < n; i++)
	{
		for (j = 0; j < m; j++)
			f >> a[i][j];
	}
	return a;
}
void show(ofstream &f, int**x, int n, int m)
{
	int i, j;
	for (i = 0; i < n; i++)
	{
		for (j = 0; j < m; j++)
			f << setw(5) << x[i][j];
		f << endl;
	}
}
void sum(int**x, int**y, int**z, int n, int m)
{

	int i, j;
	for (i = 0; i < n; i++)
		for (j = 0; j < m; j++)
			z[i][j] = x[i][j] + y[i][j];

}
void difference(int**x, int**y, int**z, int n, int m)
{
	int i, j;
	for (i = 0; i < n; i++)
		for (j = 0; j < m; j++)
			z[i][j] = x[i][j] + (-1)*y[i][j];

}
void mult(ofstream &f, int**x, int**y, int n, int m, int n1, int m1)

{
	if (m != n1)
		cout << "Can't find mult!";
	else
	{
		int i, j, **z;
		z = new int*[n];
		for (i = 0; i < m1; i++)
			z[i] = new int[m1];
		for (i = 0; i < n; i++)
		{
			for (j = 0; j < m1; j++)
			{
				z[i][j] = 0;
				for (int k = 0; k < m; k++)
					z[i][j] += x[i][k] * y[k][j];
				f << z[i][j] << " ";

			}
			f << endl;
		}










	}

}

void kmult(ofstream &f, int**x, int n, int m)
{
	int i, j, k;
	cout << "Vvedite k=";
	cin >> k;
	for (i = 0; i < n; i++)
	{
		for (j = 0; j < m; j++)
		{
			x[i][j] *= k;
			f << x[i][j] << " ";
		}

		f << endl;
	}

}


int main()
{
	ifstream matr("matrica.txt");
	ofstream r("rezultat.txt");
	if (!matr)
	{
		cout << "Can't open matrica.txt";
		exit(-1);
	}

	int n, m, n1, m1;
	cout << "Vvedite n=";
	cin >> n;
	cout << "Vvedite m=";
	cin >> m;
	cout << "VVedite n1=";
	cin >> n1;
	cout << "Vvedite m1=";
	cin >> m1;
	int**a, **b, **c;
	a = create(matr, n, m);
	b = create(matr, n1, m1);
	c = new int*[n];
	int i;
	for (i = 0; i < m; i++)
		c[i] = new int[n];
	matr.close();
	r << "Mult a*b=" << endl;
	mult(r, a, b, n, m, n1, m1);
	r << "Kmult k*a=" << endl;
	kmult(r, a, n, m);
	r << "Kmult k*b=" << endl;
	kmult(r, b, n1, m1);
	r << endl;
	if (n == n1 && m == m1)
	{sum(a, b, c, n, m);
		r << "Summa a+b=" << endl;
		show(r, c, n, m);
		difference(a, b, c, n, m);
		r << "Difference a-b=" << endl;
		show(r, c, n, m);
		r.close();
	}
	else
		cout << "Can't find sum and difference";


}