#include "Matrix.h"

void minor(matrix *m, short delete_row, short delete_col, matrix *ans);
void minor(matrix *m, short delete_row, short delete_col, matrix *ans)
{	short rr, ra, cc, ca;

/*  Create space for answer matrix here */
/*  FAILS if 
	delete_row is not between 0 and m->rows-1
	delete_col is not between 0 and m->cols-1
	m->rows==1 or m->cols==1
*/
NewMatrix(ans,m->rows-1,m->cols-1);
for(rr=0, ra=0; rr<m->rows; rr++) {
	if(rr==delete_row) continue;
	for(cc=0,ca=0;cc<m->cols;cc++) {
	if(cc==delete_col) continue;
	ans->st[ans->cols*ra+ca]=m->st[m->cols*rr+cc];
	ca++;
  	 }
   ra++;
   }
}


short det(matrix *m);
/* FAILS if matrix is not square */


short det(matrix *m)
{	short	ans, cc, sign;
	matrix	tmp;

if(m->rows==1) return m->st[0];
ans=0;
for(cc=0, sign=1;cc<m->cols;cc++, sign=-sign) {
	minor(m,0,cc,&tmp);
	ans+=sign*m->st[cc]*det(&tmp);
	DisposeMatrix(&tmp);
	}
return ans;
}