Code:

int Determinant(int m[DIM][DIM],int size);
int Cofactor(int m[DIM][DIM],int row,int col,int size);
int i,j,c,r;
void main()
{
int a[DIM][DIM] = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int b[DIM][DIM] = {
{1, 2, 3, 4},
{4, 5, 7, 8},
{9, 0, 1, 2},
{3, 4, 5, 6},
};
printf("det a=%d\n",Determinant(a,3));
printf("det b=%d\n",Determinant(b,4));
}
int Determinant(int m[DIM][DIM], int size) {
if (size < 2) return 0;
if (size == 2) {
return m[0][0] * m[1][1] - m[0][1] * m[1][0];
}
int d = 0;
for (i=0; i<size; i++)
d += m[0][i] * Cofactor(m, 0, i, size);
return d;
}
int Cofactor(int m[DIM][DIM], int row, int col, int size) {
int m2[DIM][DIM];
for (i=0,r=0; i<size; i++) {
if (i==row) continue;
for (j=0,c=0; j<size; j++) {
if (j==col) continue;
m2[r][c] = m[i][j];
c++;
}
r++;
}
return Determinant(m2,size-1) * (((row+col)%2==0)? 1 : (-1));
}