From 048bfd21692ea794d01319276796aca759974d8a Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Mon, 4 Nov 2024 22:30:33 +0000
Subject: [PATCH] Rewrite solve procedure to be iterative instead of recursive

---
 main.c | 64 ++++++++++++++++++++++++++++++----------------------------
 1 file changed, 33 insertions(+), 31 deletions(-)

diff --git a/main.c b/main.c
index daebc65..0df5c43 100644
--- a/main.c
+++ b/main.c
@@ -127,41 +127,42 @@ static void generate(vec2_t p)
 	} while (sp != stack);
 }
 
-static bool solve(vec2_t start, vec2_t *path, vec2_t **end)
+static void solve(vec2_t p, vec2_t *sp, vec2_t **end)
 {
-	*path++ = start;
+	*sp++ = p;
+	while (1) {
+		if (GOAL == p.x && GOAL == p.y) {
+			*sp++ = p;
+			*end = sp;
+			return;
+		}
 
-	for (int i = 0; i < 4; ++i) {
-		const vec2_t next = {
-			.x = start.x + steps[i].x,
-			.y = start.y + steps[i].y,
-		};
-		const vec2_t im = {
-			.x = (start.x + next.x) / 2,
-			.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;
+		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;
 
-		if (x_in_bounds && y_in_bounds) {
-			const bool accessible = maze[im.x][im.y].is_path;
-			const bool unvisited = !maze[next.x][next.y].visited;
-			if (accessible && unvisited) {
-				maze[next.x][next.y].visited = true;
-				maze[im.x][im.y].visited = true;
-				if (GOAL == next.x && GOAL == next.y) {
-					*path++ = next;
-					*end = path;
-					return true;
-				}
-				if (solve(next, path, end))
-					return true;
+			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;
 			}
 		}
-	}
 
-	--path;
-	return false;
+		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)
@@ -221,11 +222,12 @@ int main(void)
 		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);
 		solve(solve_start, path, &path_end);
 
+		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 = {