Draw shortest path to exit instead of all visited cells

main.c

@@ -24,6 +24,7 @@
 #define PX(x) ((x) << 3)
 
 #define GOAL (GRID_SIZE - 1)
+#define MAX_PATH_LENGTH (MAZE_SIZE * MAZE_SIZE)
 
 typedef enum { LEFT, RIGHT, UP, DOWN } dir_t;
 
@@ -111,8 +112,10 @@ static void generate(vec2_t start)
 	}
 }
 
-static bool solve(vec2_t start)
+static bool solve(vec2_t start, vec2_t *path, vec2_t **end)
 {
+	*path++ = start;
+
 	for (int i = 0; i < 4; ++i) {
 		const vec2_t next = {
 			.x = start.x + steps[i].x,
@@ -130,17 +133,19 @@ static bool solve(vec2_t start)
 			const bool unvisited = !maze[next.x][next.y].visited;
 			if (accessible && unvisited) {
 				maze[next.x][next.y].visited = true;
-				draw_visited(next);
 				maze[im.x][im.y].visited = true;
-				draw_visited(im);
-
-				nanosleep(&solve_pause, NULL);
-				if ((GOAL == next.x && GOAL == next.y) || solve(next))
+				if (GOAL == next.x && GOAL == next.y) {
+					*path++ = next;
+					*end = path;
+					return true;
+				}
+				if (solve(next, path, end))
 					return true;
 			}
 		}
 	}
 
+	--path;
 	return false;
 }
 
@@ -199,15 +204,25 @@ int main(void)
 
 		// 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);
-		solve(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);
+		// Draw solution path
+		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);
 	}