Find determinant of a NxN matrix (square matrix)

determinant.c

#include <stdio.h>
#include <stdlib.h>
/* 1 2 3 5
   3 4 5 6
   6 7 8 7
   2 3 4 5
*/
int deterstandard(const int order,int **matrix)
{
    int i,j,k,val=0;
    if (order ==2) return val+(deter(matrix));
    int (*tmp)[order]=(int (*)[order])matrix;
    //print

    for (k=0;k<order;k++)
    {

        int tmpmatrix[order-1][order-1];
        int r=0,c=0;
        for (i=1;i<order;i++)
        {

            for (j=0;j<order;j++)
            {
                if (j==k) continue;
                tmpmatrix[r][c++] = tmp[i][j];

            }

            if (c==order-1)
            {
                r++;
                c=0;
            }
        }

        int sign=((k+1) %2 ==0)?-1:1;
        val += sign * tmp[0][k] *deterstandard(order-1,tmpmatrix);
        //print
    }
    return val;
}


int deter( int (*arr)[2])
{
    int i;
    int val1=1,val2=1;
    for (i=0;i<2;i++)
    {
        val1 *=arr[i][i];
        val2 *=arr[i][2-i-1];

    }
    return val1-val2;
}

int main()
{
    int n,i,j;
    printf("Enter order of square matrix: ");
    scanf("%d",&n);
    int mat[n][n];
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            printf("(%d,%d): ",i+1,j+1);

            scanf("%d",&mat[i][j]);
        }
    }
    printf("\nDeterminant: %d\n",deterstandard(n,mat));
}