Sidewinder maze instead of dfs

maze.c

@@ -34,6 +34,13 @@
 #define MAZEENDGAP (MAZESIZE / 5)
 #define HSCALE 1.5
 #define PAINTINGODDS 20
+// Some arbitrarily large number, up to you
+#define MAZEHRAND 100
+// The horizontal choice will be this out of MAZEHRAND.
+// So, if MAZEHRAND is 100, setting this to 80 will mean
+// an 8 / 10 chance to go horizontal
+#define MAZEHBIAS 60
+#define PRINTMAZE
 
 // Maze grows in the positive direction
 #define MAZENORTH 1
@@ -157,69 +164,29 @@ void maze_generate(uint8_t *maze, int size, struct vec2i *start,
   for (int i = 0; i < mazesquare; i++) {
     maze[i] = MAZENORTH | MAZEEAST;
   }
-  int *mazestack;
-  mallocordie(mazestack, sizeof(int) * mazesquare);
-  for (int i = 0; i < size * size; i++) {
-    mazestack[i] = -1;
-  }
-  // Push current cell onto stack, mark as visited
+
   start->x = rand() % size;
   start->y = rand() % size;
-  int x = start->x;
-  int y = start->y;
-  int mazetop = 0;
-  int maxmazetop = 0;
-  STACKPUSH(mazestack, mazetop, x + y * size);
-  maze[x + y * size] |= MAZEVISIT;
-  uint8_t visitable[4];
-  int visittop = 0;
 
-  // Now let's make a maze!
-  while (mazetop) {
-    // The end of the maze is the furthest into the stack we go. This should
-    // somewhat maximize the complexity of start to finish?
-    if (mazetop > maxmazetop) {
-      //   end->x =  x;
-      //   end->y =  y;
-      maxmazetop = mazetop;
-    }
-    mazetop--;
-    visittop = 0;
-    x = mazestack[mazetop] % size;
-    y = mazestack[mazetop] / size;
-    if (x > 0 && !maze_visited(maze, x - 1, y, size)) {
-      visitable[visittop++] = DIRWEST;
-    }
-    if (x < size - 1 && !maze_visited(maze, x + 1, y, size)) {
-      visitable[visittop++] = DIREAST;
-    }
-    if (y > 0 && !maze_visited(maze, x, y - 1, size)) {
-      visitable[visittop++] = DIRSOUTH;
-    }
-    if (y < size - 1 && !maze_visited(maze, x, y + 1, size)) {
-      visitable[visittop++] = DIRNORTH;
-    }
-    // You can generate a random location!
-    if (visittop) {
-      // Readd ourselves, we're moving
-      STACKPUSH(mazestack, mazetop, x + y * size);
-      uint8_t dir = visitable[rand() % visittop];
-      struct vec2i movedir = dirtovec(dir);
-      int nx = x + movedir.x;
-      int ny = y + movedir.y;
-      // Trust that the visitable array is always valid
-      if (dir == DIREAST) { // Tear down east wall
+  // Extremely simple sidewinder algorithm. Because the maze grows northeast, we
+  // actually have to start from the end and work backwards
+  for (int y = size - 1; y >= 0; y--) {
+    if (y == size - 1) {
+      for (int x = 0; x < size - 1; x++) {
+        maze[x + y * size] &= ~MAZEEAST;
+      }
+      continue;
+    }
+    int xs = 0;
+    for (int x = 0; x < size; x++) {
+      // If we decide to stop (or it's the end), find a place in our
+      // current span to carve north
+      if ((x == size - 1) || ((rand() % MAZEHRAND) > MAZEHBIAS)) {
+        maze[xs + (rand() % (x - xs + 1)) + y * size] &= ~MAZENORTH;
+        xs = x + 1;
+      } else {
         maze[x + y * size] &= ~MAZEEAST;
-      } else if (dir == DIRWEST) { // Move left and tear down east wall
-        maze[(x - 1) + y * size] &= ~MAZEEAST;
-      } else if (dir == DIRNORTH) { // tear down north wall
-        maze[x + y * size] &= ~MAZENORTH;
-      } else if (dir == DIRSOUTH) { // move down and tear down north wall
-        maze[x + (y - 1) * size] &= ~MAZENORTH;
       }
-      // Push onto stack and set visited
-      STACKPUSH(mazestack, mazetop, nx + ny * size);
-      maze[nx + ny * size] |= MAZEVISIT;
     }
   }
 
@@ -229,10 +196,22 @@ void maze_generate(uint8_t *maze, int size, struct vec2i *start,
   } while (abs(end->x - start->x) < MAZEENDGAP &&
            abs(end->y - start->y) < MAZEENDGAP);
 
-  eprintf("Maze generate: %d,%d -> %d,%d maxdepth: %d\n", start->x, start->y,
-          end->x, end->y, maxmazetop);
+#ifdef PRINTMAZE
+  char line[MAZESIZE * 4]; // IDK, just in case
+  // -1 because we draw the top line
+  for (int y = -1; y < size; y++) {
+    for (int x = size - 1; x >= 0; x--) {
+      line[x * 2] = (y == -1 || maze[x + y * size] & MAZENORTH) ? '_' : ' ';
+      line[x * 2 + 1] =
+          (y == -1 || (maze[x + y * size] & MAZEEAST) == 0) ? ' ' : '|';
+    }
+    line[size * 2] = 0;
+    eprintf("|%s\n", line);
+  }
+#endif
 
-  free(mazestack);
+  eprintf("Maze generate: %d,%d -> %d,%d\n", start->x, start->y, end->x,
+          end->y);
 }
 
 // int rand_painting(int size) {