Passing a matrix in a function (C)

Question

I have an issue passing a matrix to a function in C. There is the function I want to create:

void ins (int *matrix, int row, int column);

b

Answer 1

C - allocating a matrix in a function

Above you will find a program that I have made with functions allocating and manipulating matrices in any possible way for C (gcc C11/C99).

Answer 2

Much better way to use malloc function and create dynamically allocated array and do whatever you want to do using 2d array:

#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>

void fun(int **arr,int m,int n)
{
    int i, j;
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
            scanf("%d", &arr[i][j]);
        }
    }

}

int main()
{
    int i,j,m,n;
    printf("enter order of matrix(m*n)");
    scanf("%d*%d",&m,&n);
    int **a=(int **)malloc(m*sizeof(int));
    for(i=0;i<n;i++)
        a[i]=(int *)malloc(n*sizeof(int));

    fun(a,m,n);
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
        printf("%d ", a[i][j]);
        }
        printf("\n");

    }
    return 0;
}

 output:
     #include <stdio.h>
#include <stdlib.h>
#include <stdio.h>

void fun(int **arr,int m,int n)
{
    int i, j;
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
            scanf("%d", &arr[i][j]);
        }
    }

}

int main()
{
    int i,j,m,n;
    printf("enter order of matrix(m*n)");
    scanf("%d*%d",&m,&n);
    int **a=(int **)malloc(m*sizeof(int));
    for(i=0;i<n;i++)
        a[i]=(int *)malloc(n*sizeof(int));

    fun(a,m,n);
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
        printf("%d ", a[i][j]);
        }
        printf("\n");

    }
    return 0;
}

Answer 3

If you have a modern C compiler you can do the following for 2D matrices of any sizes

void ins (size_t rows, size_t columns, int matrix[rows][columns]);

Important is that the sizes come before the matrix, such that they are known, there.

Inside your function you then can access the elements easily as matrix[i][j] and the compiler is doing all the index calculations for you.

Answer 4

it would also possible to leave the first dimension empty, the same as (*matrix):

void ins (int matrix[][100], int row, int column);

Answer 5

You need to pass a pointer with as much levels of indirection (*) as the number of dimensions of your matrix.

For example, if your matrix is 2D (e.g. 10 by 100), then:

void ins (int **matrix, int row, int column);

If you have a fixed dimension (e.g. 100), you can also do:

void ins (int (*matrix)[100], int row, int column);

or in your case:

void ins (int (*matrix)[SIZE], int row, int column);

If both your dimensions are fixed:

void ins (int matrix[10][100], int row, int column);

or in your case:

void ins (int matrix[SIZE][SIZE], int row, int column);