The memory of a dynamic matrix can be allocated at run time as opposite to the static matrices (who are allocated at compile-time).
/*
* Description:
* Allocates dinamically memory for a rows x columns matrix
* Parameters:
* matrix - a pointer to the matrix which will be allocated
* rows - the number of rows
* columns - the number of columns
* Returns:
* matrix - a pointer to the allocated matrix
*/
int** Matrix_Alloc(int** matrix, int rows, int columns)
{
int i;
matrix=malloc(sizeof(int)*rows*columns);
if(matrix!=NULL)
{
/*Allocating space for each row*/
for(i=0; i<rows;i++)
{
matrix[i] = malloc(sizeof(int)*columns);
if(matrix[i]==NULL)
{
return NULL;
}
}
}
return matrix;
}
/*
* Description:
* Frees a dynamically allocated matrix
* Parameters:
* matrix - a pointer to an allocated matrix
* rows - the number of rows
* columns - the number of columns
* Returns:
* Nothing
*/
void Matrix_Free(int** matrix, int rows)
{
int i;
for(i = 0; i < rows; i++)
{
free(matrix[i]);
}
free(matrix);
}
Here's an example on how to use the functions:#include<stdio.h>
#include<stdbool.h>
#include<stdlib.h>
int** Matrix_Alloc(int** matrix, int rows, int columns);
void Matrix_Free(int** matrix, int rows);
void Matrix_Print(int** matrix, int rows, int columns)
{
int i,j;
for(i=0; i<rows;i++)
{
for(j=0; j<columns; j++)
{
printf("%d ",matrix[i][j]);
}
putchar('\n');
}
}
int main(void)
{
int **matrix = NULL;
int i, j;
/*Allocating the matrix*/
matrix = Matrix_Alloc(matrix, 3, 3);
/*Assigning values to the matrix*/
for (i = 0; i < 3; i++)
{
for (j = 0; j < 3; j++)
{
matrix[i][j] = (i+j);
}
}
/*Printing the results*/
Matrix_Print(matrix,3,3);
/*Freeing the memory*/
Matrix_Free(matrix,3);
puts("Memory freed");
return 0;
}
/*Output
0 1 2
1 2 3
2 3 4
Memory freed
*/
In the example above we used a primitive data type. If we would had use a structure, each element of the matrix would had to be allocated/freed as well.
