Increase maze size and decrease cell size

main.c

@@ -14,16 +14,19 @@
 #include <time.h>
 #include <unistd.h>
 
-#define MAZE_SIZE 24
+#define MAZE_SIZE 100
 
 #define GRID_SIZE (2 * MAZE_SIZE - 1)
 #define MARGIN 2
 #define WALL_THICKNESS 1
 #define WINDOW_SIZE (GRID_SIZE + 2 * (WALL_THICKNESS + MARGIN))
 
-#define PX(x) ((x) << 3)
+#define PX(x) ((x) << 2)
 
 #define GOAL (GRID_SIZE - 1)
+#define MAX_PATH_LENGTH (MAZE_SIZE * MAZE_SIZE)
+
+#define STACK_SIZE (MAZE_SIZE * MAZE_SIZE)
 
 typedef enum { LEFT, RIGHT, UP, DOWN } dir_t;
 
@@ -39,7 +42,8 @@ typedef struct {
 	bool visited : 1;
 } cell_t;
 
-static const struct timespec wait = { .tv_nsec = 5000000 };
+static const struct timespec gen_pause = { .tv_nsec = 1000000 };
+static const struct timespec solve_pause = { .tv_nsec = 4000000 };
 
 static const vec2_t steps[] = {
 	[LEFT] = { .x = -2, .y = 0 },
@@ -73,65 +77,92 @@ static void draw_visited(vec2_t p)
 	XFlush(dpy);
 }
 
-static bool
-random_walk(coord_pred_t should_visit, visit_fn_t visit_fn, vec2_t start)
+static bool in_bounds(vec2_t p)
 {
-	dir_t visit[] = { LEFT, RIGHT, UP, DOWN };
-	for (int i = 3; i > 0; --i) {
-		const int r = rand() % (i + 1);
-		const dir_t tmp = visit[r];
-		visit[r] = visit[i];
-		visit[i] = tmp;
-	}
+	const bool valid_x = p.x >= 0 && p.x < GRID_SIZE;
+	const bool valid_y = p.y >= 0 && p.y < GRID_SIZE;
+	return valid_x && valid_y;
+}
 
-	vec2_t next, im;
+static bool finished_gen(vec2_t p)
+{
+	vec2_t n;
 	for (int i = 0; i < 4; ++i) {
-		next.x = start.x + steps[visit[i]].x;
-		next.y = start.y + steps[visit[i]].y;
-		im.x = (start.x + next.x) / 2;
-		im.y = (start.y + next.y) / 2;
-
-		const bool x_in_bounds = next.x >= 0 && next.x < GRID_SIZE;
-		const bool y_in_bounds = next.y >= 0 && next.y < GRID_SIZE;
-		if (x_in_bounds && y_in_bounds && should_visit(next, im)) {
-			if (visit_fn(next, im)
-			    || random_walk(should_visit, visit_fn, next))
-				return true;
-		}
+		n.x = p.x + steps[i].x;
+		n.y = p.y + steps[i].y;
+		if (in_bounds(n) && !maze[n.x][n.y].is_path)
+			return false;
 	}
-
-	return false;
+	return true;
 }
 
-static bool is_wall(vec2_t c, vec2_t im)
+static void generate(vec2_t p)
 {
-	(void)im;
-	return !maze[c.x][c.y].is_path;
+	vec2_t stack[STACK_SIZE], *sp = stack;
+	do {
+		if (finished_gen(p)) {
+			p = *(--sp);
+			continue;
+		}
+
+		vec2_t n;
+		do {
+			dir_t d = rand() % 4;
+			n.x = p.x + steps[d].x;
+			n.y = p.y + steps[d].y;
+		} while (!in_bounds(n) || maze[n.x][n.y].is_path);
+
+		const vec2_t im = {
+			.x = (p.x + n.x) / 2,
+			.y = (p.y + n.y) / 2,
+		};
+		maze[im.x][im.y].is_path = maze[n.x][n.y].is_path = true;
+		clear_path(im);
+		clear_path(n);
+
+		*sp++ = p;
+		p = n;
+
+		nanosleep(&gen_pause, NULL);
+	} while (sp != stack);
 }
 
-static bool generation_visit(vec2_t c, vec2_t im)
+static void solve(vec2_t p, vec2_t *sp, vec2_t **end)
 {
-	maze[c.x][c.y].is_path = true;
-	maze[im.x][im.y].is_path = true;
-	clear_path(im);
-	clear_path(c);
-	nanosleep(&wait, NULL);
-	return false;
-}
+	*sp++ = p;
+	while (1) {
+		if (GOAL == p.x && GOAL == p.y) {
+			*sp++ = p;
+			*end = sp;
+			return;
+		}
 
-static bool accessible_and_unvisited(vec2_t c, vec2_t im)
-{
-	return maze[im.x][im.y].is_path && !maze[c.x][c.y].visited;
-}
+		vec2_t n, im;
+		bool got_n = false;
+		for (int i = 0; i < 4; ++i) {
+			n.x = p.x + steps[i].x;
+			n.y = p.y + steps[i].y;
+			if (!in_bounds(n))
+				continue;
 
-static bool solve_visit(vec2_t c, vec2_t im)
-{
-	maze[c.x][c.y].visited = true;
-	maze[im.x][im.y].visited = true;
-	draw_visited(im);
-	draw_visited(c);
-	nanosleep(&wait, NULL);
-	return GOAL == c.x && GOAL == c.y;
+			im.x = (p.x + n.x) / 2;
+			im.y = (p.y + n.y) / 2;
+			if (maze[im.x][im.y].is_path && !maze[n.x][n.y].visited) {
+				got_n = true;
+				break;
+			}
+		}
+
+		if (!got_n) {
+			p = *(--sp);
+			continue;
+		}
+
+		maze[im.x][im.y].visited = maze[n.x][n.y].visited = true;
+
+		*sp++ = p;
+		p = n;
+	}
 }
 
 int main(void)
@@ -185,19 +216,30 @@ int main(void)
 		const vec2_t gen_start = { GOAL, GOAL };
 		maze[GOAL][GOAL].is_path = true;
 		clear_path(gen_start);
-		random_walk(is_wall, generation_visit, gen_start);
+		generate(gen_start);
 
 		// Solve
 		const vec2_t solve_start = { 0, 0 };
+		vec2_t path[MAX_PATH_LENGTH], *path_end;
 		maze[0][0].visited = true;
-		XSetForeground(dpy, ctx, visited_col);
-		draw_visited(solve_start);
-		random_walk(accessible_and_unvisited, solve_visit, solve_start);
+		solve(solve_start, path, &path_end);
 
-		// Draw exit path
-		const int x = PX(MARGIN + GRID_SIZE + 1), y = PX(MARGIN + GRID_SIZE);
-		XFillRectangle(dpy, window, ctx, x, y, PX(1), PX(1));
-		XFlush(dpy);
+		sleep(1);
+
+		// Draw solution path
+		XSetForeground(dpy, ctx, visited_col);
+		const vec2_t *prev = &solve_start;
+		for (const vec2_t *p = path; p < path_end; ++p) {
+			const vec2_t im = {
+				.x = (prev->x + p->x) / 2,
+				.y = (prev->y + p->y) / 2,
+			};
+			draw_visited(*p);
+			draw_visited(im);
+			nanosleep(&solve_pause, NULL);
+			prev = p;
+		}
+		draw_visited(exit);
 
 		sleep(1);
 	}