Initial Commit

Gemfile

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+source 'https://rubygems.org'
+
+gem 'chunky_png'

binary_tree.rb

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+class BinaryTree
+  def self.on(grid)
+    grid.each_cell do |cell|
+      neighbors = []
+      neighbors << cell.north if cell.north
+      neighbors << cell.east if cell.east
+
+      neighbor = neighbors.sample
+
+      cell.link(neighbor) if neighbor
+
+    end
+
+    grid
+  end
+end

binary_tree_demo.rb

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+require "grid"
+require "binary_tree"
+
+grid = Grid.new(6, 10)
+BinaryTree.on(grid)
+
+puts grid
+img = grid.to_png
+img.save "bt.png"

cell.rb

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+class Cell
+  attr_reader :row, :column
+  attr_accessor :north, :south, :east, :west
+
+  def initialize(row, column)
+    @row, @column = row, column
+    @links = {}
+  end
+
+  def link(cell, bidi=true)
+    @links[cell] = true
+    cell.link(self, false) if bidi
+    self
+  end
+
+  def unlink(cell, bidi=true)
+    @links.delete(cell)
+    cell.unlink(self, false) if bidi
+    self
+  end
+
+  def links
+    @links.keys
+  end
+
+  def linked?(cell)
+    @links.key?(cell)
+  end
+
+  def neighbors
+    list = []
+    list << north if north
+    list << south if south
+    list << east if east
+    list << west if west
+    list
+  end
+end

grid.rb

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+require "cell"
+require "chunky_png"
+
+class Grid
+  attr_reader :rows, :columns
+
+  def initialize(rows, columns)
+    @rows = rows
+    @columns = columns
+
+    @grid = prepare_grid
+    configure_cells
+  end
+
+  def prepare_grid
+    Array.new(rows) do |row|
+      Array.new(columns) do |column|
+        Cell.new(row, column)
+      end
+    end
+  end
+
+  def configure_cells
+    each_cell do |cell|
+      row, col = cell.row, cell.column
+
+      cell.north = self[row - 1, col]
+      cell.south = self[row + 1, col]
+      cell.west = self[row, col - 1]
+      cell.east = self[row, col + 1]
+    end
+  end
+
+  def [](row, column)
+    return nil unless row.between?(0, @rows - 1)
+    return nil unless column.between?(0, @grid[row].count - 1)
+    @grid[row][column]
+  end
+
+  def random_cell
+    row = rand(@rows)
+    column = rand(@grid[row].count)
+
+    self[row, column]
+  end
+
+  def size
+    @rows * @columns
+  end
+
+  def each_row
+    @grid.each do |row|
+      yield row
+    end
+  end
+
+  def each_cell
+    each_row do |row|
+      row.each do |cell|
+        yield cell if cell
+      end
+    end
+  end
+
+
+  def to_s
+    output = "+" + "---+" * columns + "\n"
+    corner = "+"
+
+    each_row do |row|
+      top = "|"
+      bottom = "+"
+
+      row.each do |cell|
+        cell = Cell.new(-1, -1) unless cell
+        body = "   "
+        east_boundary = (cell.linked?(cell.east) ? " " : "|")
+        top << body << east_boundary
+
+        south_boundary = (cell.linked?(cell.south) ? "   " : "---")
+        bottom << south_boundary << corner
+      end
+
+      output << top << "\n"
+      output << bottom << "\n"
+    end
+
+    output
+  end
+
+  def to_png(cell_size: 10)
+    img_width = cell_size * columns
+    img_height = cell_size * rows
+
+    background = ChunkyPNG::Color::WHITE
+    wall = ChunkyPNG::Color::BLACK
+
+    img = ChunkyPNG::Image.new(img_width + 1, img_height + 1, background)
+
+    each_cell do |cell|
+      x1 = cell.column * cell_size
+      y1 = cell.row * cell_size
+      x2 = (cell.column+1) * cell_size
+      y2 = (cell.row+1) * cell_size
+
+      img.line(x1, y1, x2, y1, wall) unless cell.north
+      img.line(x1, y1, x1, y2, wall) unless cell.west
+      img.line(x2, y1, x2, y2, wall) unless cell.linked?(cell.east)
+      img.line(x1, y2, x2, y2, wall) unless cell.linked?(cell.south)
+    end
+
+    img
+
+  end
+
+end

sidewinder.rb

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+class Sidewinder
+  def self.on(grid)
+    grid.each_row do |row|
+      run = []
+      row.each do |cell|
+        run << cell
+
+        at_eastern_boundary = (cell.east == nil)
+        at_northern_boundary = (cell.north == nil)
+
+        should_close_out = at_eastern_boundary || (!at_northern_boundary && rand(2) == 0)
+
+        if should_close_out
+          member = run.sample
+          member.link(member.north) if member.north
+          run.clear
+        else
+          cell.link(cell.east)
+        end
+
+      end
+    end
+
+    grid
+  end
+end

sidewinder_demo.rb

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+require "grid"
+require "sidewinder"
+
+grid = Grid.new(6, 10)
+Sidewinder.on(grid)
+
+puts grid
+img = grid.to_png
+img.save "sw.png"