/* Advance the solution marking by one cell. */
void maze_mark_advance_cell(struct maze *mp, int cr, int cc, int *nr, int *nc)
{
cell_t *cp = maze_get_cell_addr(mp, cr, cc);
*cp |= SOLUTION;
if (maze_get_cell_distance(mp, cr, cc) == 1)
ABORT();
if (!maze_is_prev_cell(mp, cr, cc, cr - 1, cc, nr, nc) &&
!maze_is_prev_cell(mp, cr, cc, cr + 1, cc, nr, nc) &&
!maze_is_prev_cell(mp, cr, cc, cr, cc - 1, nr, nc) &&
!maze_is_prev_cell(mp, cr, cc, cr, cc + 1, nr, nc))
ABORT();
}
/*
* Mark the maze's solution, working from the end to the beginning.
* Returns the length of the solution, including the two endpoints.
* A length of zero implies an unsolvable maze.
*/
int maze_mark_solution(struct maze *mp, int startrow, int startcol,
int endrow, int endcol)
{
int cr;
int cc;
cell_t *cp;
int nr = endrow;
int nc = endcol;
for (;;) {
cr = nr;
cc = nc;
cp = maze_get_cell_addr(mp, cr, cc);
*cp |= SOLUTION;
if (cr == startrow && cc == startcol)
return maze_get_cell_distance(mp, endrow, endcol);
if (!maze_is_prev_cell(mp, cr, cc, cr - 1, cc, &nr, &nc) &&
!maze_is_prev_cell(mp, cr, cc, cr + 1, cc, &nr, &nc) &&
!maze_is_prev_cell(mp, cr, cc, cr, cc - 1, &nr, &nc) &&
!maze_is_prev_cell(mp, cr, cc, cr, cc + 1, &nr, &nc))
ABORT();
}
}
