Sidewinder algorithm

Author: Kartones

README.md

@@ -2,7 +2,14 @@
 
 ## Introduction
 
-I'm reading the [Mazes for Programmers](http://www.mazesforprogrammers.com) book, but source code comes in Ruby and I like Python, so I decided to rewrite them as I read. And along the way add tests, both to make sure the conversion is ok and to see a more continuous way than having to write all basic stuff and an "ASCII renderer" to see anything.
+I'm reading the [Mazes for Programmers](http://www.mazesforprogrammers.com) book, but source code comes in Ruby and I like Python, so I decided to rewrite them as I read. And along the way add tests, both to make sure the conversion is ok and to see a more continuous way than having to write all basic stuff and an "ASCII renderer" before being able to see anything.
+
+## Implemented algorithms
+
+- Binary Tree
+- Sidewinder
+
+Note: This list will grow as I progress with the book.
 
 ## Setup
 

algorithms/binary_tree.py

@@ -1,12 +1,10 @@
 from random import choice
 
-from typing import List, Union  # noqa: F401
-
-from base.cell import Cell   # noqa: F401
 from base.grid import Grid
 
 """
-A binary tree visits each cell in the grid and chooses to carve a passage either north or east.
+A binary tree visits each cell in the grid and chooses to carve a passage either north or east with a simple random.
+Causes topmost row and rightmost column to always be straight lines.
 """
 
 
@@ -15,7 +13,7 @@ class BinaryTree:
     @staticmethod
     def on(grid: Grid) -> Grid:
         for cell in grid.each_cell():
-            neighbors = []         # type: List[Union[None, Cell]]
+            neighbors = []
             if cell.north:
                 neighbors.append(cell.north)
             if cell.east:

algorithms/sidewinder.py

@@ -0,0 +1,30 @@
+from random import randint, choice
+
+from base.grid import Grid
+
+"""
+A sidewinder visits each cell in the grid and chooses to carve a passage either north or east (similar to Binary Tree),
+but running row by row.
+Causes topmost row to always be a straight line.
+"""
+
+
+class Sidewinder:
+
+    @staticmethod
+    def on(grid: Grid) -> Grid:
+        for row in grid.each_row():
+            run = []
+            for cell in row:
+                run.append(cell)
+                at_eastern_boundary = cell.east is None
+                at_northen_boundary = cell.north is None
+                should_close_out = at_eastern_boundary or (not at_northen_boundary and randint(0, 1) == 0)
+                if should_close_out:
+                    member = choice(run)
+                    if member.north:
+                        member.link(member.north)
+                    run = []
+                else:
+                    cell.link(cell.east)
+        return grid

base/cell.py

@@ -58,6 +58,8 @@ def neighbors(self) -> List[Union[None, "Cell"]]:
             neighbors_list.append(self.west)
         return neighbors_list
 
+    # The following methods actually lie because don't take into account neighbors/linked-cells, but for now is enough
+
     def __hash__(self) -> int:
         return hash((self.column, self.row))
 

demos/sidewinder_demo.py

@@ -0,0 +1,10 @@
+
+from base.grid import Grid
+from algorithms.sidewinder import Sidewinder
+from renderers.ascii_renderer import ASCIIRenderer
+
+
+if __name__ == "__main__":
+    grid = Grid(6, 6)
+    grid = Sidewinder.on(grid)
+    ASCIIRenderer.render(grid)