Faster maze generation for acmaze

apps.json

@@ -5665,8 +5665,8 @@
   { "id": "acmaze",
     "name": "AccelaMaze",
     "shortName":"AccelaMaze",
-    "version":"0.01",
+    "version":"0.02",
-    "description": "Tilt the watch to roll a ball through a maze",
+    "description": "Tilt the watch to roll a ball through a maze.",
     "icon": "app.png",
     "tags": "game",
     "supports" : ["BANGLEJS2"],

apps/acmaze/ChangeLog

@@ -1 +1,2 @@
 0.01: New App!
+0.02: Faster maze generation

apps/acmaze/app.js

@@ -35,21 +35,56 @@ function Maze(n) {
     this.walls[cell] = WALL_RIGHT|WALL_DOWN;
     this.groups[cell] = cell;
   }
+  // Candidates of walls to break when digging the maze.
+  // If candidate failed (breaking it would create a loop),
+  // it would never succeed, so no need to retry it.
+  let candidates_down = [],
+      candidates_right = [];
+  for (let r=0 ; r<n; r++) {
+    for (let c=0; c<n; c++) {
+      let cell = n*r+c;
+      if (r<(n-1)) { // Don't break wall down for bottom row.
+        candidates_down.push(cell);
+      }
+      if (c<(n-1)) { // Don't break wall right for rightmost column.
+        candidates_right.push(cell);
+      }
+    }
+  }
   let from_group, to_group;
   let ngroups = n*n;
   while (--ngroups) {
     // Abort if BTN1 pressed [grace period for menu]
     // (for some reason setWatch() fails inside constructor)
-    if (ngroups<n*n-4 && digitalRead(BTN1)) {
+    if (ngroups<n*n-16 && digitalRead(BTN1)) {
       aborting = true;
       return;
     }
     from_group = to_group = -1;
     while (from_group<0) {
-      if (Math.random()<0.5) { // try to break a wall right
+      let trying_down = false;
-        let r = Math.floor(Math.random()*n);
+      if (Math.random()<0.5 || !candidates_right.length) {
-        let c = Math.floor(Math.random()*(n-1));
+        trying_down = true;
-        let cell = r*n+c;
+      }
+      let candidates = trying_down ? candidates_down : candidates_right;
+          candidate_index = Math.floor(Math.random()*candidates.length),
+          cell = candidates.splice(candidate_index, 1)[0],
+          r = Math.floor(cell/n),
+          c = cell%n;
+      if (trying_down) { // try to break a wall down
+        if (this.groups[cell]!=this.groups[cell+n]) {
+          this.walls[cell] &= ~WALL_DOWN;
+          g.clearRect(
+              this.margin+c*this.wall_length+1,
+              this.margin+(r+1)*this.wall_length,
+              this.margin+(c+1)*this.wall_length-1,
+              this.margin+(r+1)*this.wall_length
+          );
+          g.flip(); // show progress.
+          from_group = this.groups[cell];
+          to_group = this.groups[cell+n];
+        }
+      } else { // try to break a wall right
         if (this.groups[cell]!=this.groups[cell+1]) {
           this.walls[cell] &= ~WALL_RIGHT;
           g.clearRect(
@@ -62,21 +97,6 @@ function Maze(n) {
           from_group = this.groups[cell];
           to_group = this.groups[cell+1];
         }
-      } else { // try to break a wall down
-        let r = Math.floor(Math.random()*(n-1));
-        let c = Math.floor(Math.random()*n);
-        let cell = r*n+c;
-        if (this.groups[cell]!=this.groups[cell+n]) {
-          this.walls[cell] &= ~WALL_DOWN;
-          g.clearRect(
-              this.margin+c*this.wall_length+1,
-              this.margin+(r+1)*this.wall_length,
-              this.margin+(c+1)*this.wall_length-1,
-              this.margin+(r+1)*this.wall_length
-          );
-          from_group = this.groups[cell];
-          to_group = this.groups[cell+n];
-        }
       }
     }
     for (let cell = 0; cell<n*n; cell++) {
@@ -253,7 +273,6 @@ let maze_interval = setInterval(
   function() {
     if (maze) {
       if (digitalRead(BTN1) || maze.status==STATUS_ABORTED) {
-        console.log(`aborting ${start_time}`);
         maze = null;
         start_time = duration = 0;
         aborting = false;
@@ -270,7 +289,7 @@ let maze_interval = setInterval(
         duration = Date.now()-start_time;
         g.setFontAlign(0,0).setColor(g.theme.fg);
         g.setFont("Vector",18);
-        g.drawString(`Solved in\n ${timeToText(duration)} \nClick to play again`, g.getWidth()/2, g.getHeight()/2, true);
+        g.drawString(`Solved ${maze.n}X${maze.n} in\n ${timeToText(duration)} \nClick to play again`, g.getWidth()/2, g.getHeight()/2, true);
       }
     }
   }, 25);