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An implementation of the recursive backtracking algorithm that *gasp* actually uses recursion.
# --------------------------------------------------------------------
# Recursive backtracking algorithm for maze generation. Requires that
# the entire maze be stored in memory, but is quite fast, easy to
# learn and implement, and (with a few tweaks) gives fairly good mazes.
# Can also be customized in a variety of ways.
# --------------------------------------------------------------------
# --------------------------------------------------------------------
# 1. Allow the maze to be customized via command-line parameters
# --------------------------------------------------------------------
width = (ARGV[0] || 10).to_i
height = (ARGV[1] || width).to_i
seed = (ARGV[2] || rand(0xFFFF_FFFF)).to_i
srand(seed)
grid = Array.new(height) { Array.new(width, 0) }
# --------------------------------------------------------------------
# 2. Set up constants to aid with describing the passage directions
# --------------------------------------------------------------------
N, S, E, W = 1, 2, 4, 8
DX = { E => 1, W => -1, N => 0, S => 0 }
DY = { E => 0, W => 0, N => -1, S => 1 }
OPPOSITE = { E => W, W => E, N => S, S => N }
# --------------------------------------------------------------------
# 3. The recursive-backtracking algorithm itself
# --------------------------------------------------------------------
def carve_passages_from(cx, cy, grid)
directions = [N, S, E, W].sort_by{rand}
directions.each do |direction|
nx, ny = cx + DX[direction], cy + DY[direction]
if ny.between?(0, grid.length-1) && nx.between?(0, grid[ny].length-1) && grid[ny][nx] == 0
grid[cy][cx] |= direction
grid[ny][nx] |= OPPOSITE[direction]
carve_passages_from(nx, ny, grid)
end
end
end
carve_passages_from(0, 0, grid)
# --------------------------------------------------------------------
# 4. A simple routine to emit the maze as ASCII
# --------------------------------------------------------------------
puts " " + "_" * (width * 2 - 1)
height.times do |y|
print "|"
width.times do |x|
print((grid[y][x] & S != 0) ? " " : "_")
if grid[y][x] & E != 0
print(((grid[y][x] | grid[y][x+1]) & S != 0) ? " " : "_")
else
print "|"
end
end
puts
end
# --------------------------------------------------------------------
# 5. Show the parameters used to build this maze, for repeatability
# --------------------------------------------------------------------
puts "#{$0} #{width} #{height} #{seed}"

Awesome

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