concatenate 2 matrices - c

Question

I have a matrix dynamically allocated and I want to create another one which is the first matrix but with another copy beside. for example,I have the matrix:
11
22
My new matrix will be:
1 1 1 1
2 2 2 2
How can I concatenate them? This is my code in C:
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
int **create_matrix(int row, int col)
{
int **matrix = malloc(sizeof (int*)*row);
int i;
for (i = 0; i < row; i++)
{
matrix[i] = malloc(sizeof (int)*col);
}
return matrix;
}
void matrix_input(int **matrix, int row, int col)
{
int i, j;
printf("enter the elements of the matrix:\n");
for (i = 0; i < row; i++)
{
for (j = 0; j < col; j++)
{
scanf("%d", &matrix[i][j]);
}
}
}
int **extend_matrix(int **matrix, int row, int col)
{
int k, j;
int i;
int **extend_matrix = malloc(sizeof (int*)*row);
for (k = 0; k < row + row; k++)
{
extend_matrix[k] = malloc(sizeof (int)*col);
}
extend_matrix = matrix;
extend_matrix = (int**) realloc(extend_matrix, (row + row) * sizeof (int*));
extend_matrix[j] = matrix[j];
for (i = 0; i < row; i++)
{
extend_matrix[k] = matrix[i];
}
}
void print_matrix(int **matrix, int row, int col)
{
int i, j;
for (i = 0; i < row; i++)
{
for (j = 0; j < col; j++)
{
printf(" %d ", matrix[i][j]);
}
printf("\n");
}
}
void print_extend_matrix(int **extend_matrix, int row, int col)
{
int k, j;
for (k = 0; k < row + row; k++)
{
for (j = 0; j < col; j++)
{
printf("%d", extend_matrix[k][j]);
}
printf("\n");
}
}
int main(void)
{
int **matrix;
int **extend_matrix;
int row, col;
printf("enter the number of rows of cols:");
scanf("%i%i", &row, &col);
matrix = create_matrix(row, col);
matrix_input(matrix, row, col);
print_matrix(matrix, row, col);
print_extend_matrix(extend_matrix, row, col);
getch();
return 0;
}

Answer 1

Although #NPE suggested to you a better way. If you want to allocate memory in extend_matrix()
error in your code (read comments)
int **extend_matrix = malloc(sizeof (int*)*row);
^ on row
for (k = 0; k < row + row; k++)
^ where as loop is for row + row
{
extend_matrix[k] = malloc(sizeof (int)*col); // So this cause an error,
// segment-fault
}
second, your concept is wrong to copy memory:
extend_matrix = matrix;
at this line you are assigning matrix to extend_matrix its wrong. you need loop here to copy each elements from matrix[][] to extend_matrix[][]. (but rectify your memory allocation code first)

Answer 2

I think extend_matrix() should just call create_matrix() to create a new matrix of double the width, and then use two simple nested loops to populate it.

Answer 3

If this is what you are looking for :
int concat(void * oldM, int row, int col,void& *newM) {
newM = malloc(sizeof(int)*row*col*2);
for(int i = 0;i<2;++i)
for(int j=0;j<2;++j)
newM[i][j+col] = newM[i][j] = oldM[i][j];
for(int i = 0;i<2;++i) {
for(int j=0;j<4;++j) {
cout<<"\t"<<newM[i][j];
}
cout<<"\n";
}
}