land.rb

# M is visually more dense than 'o'
M = 'land'
o = 'water'

world = [[o,o,o,o,o,o,o,o,o,o,o], 
         [o,o,o,o,M,M,o,o,o,o,o], 
         [o,o,o,o,o,o,o,o,M,M,o], 
         [o,o,o,M,o,M,M,o,o,o,o],
         [o,o,o,o,M,M,M,M,o,o,o],
         [o,o,o,M,M,M,M,M,M,M,o],
         [o,o,o,M,M,o,M,M,M,o,o],
         [o,o,o,o,o,o,M,M,o,o,o],
         [o,M,o,o,o,M,o,o,o,o,o],
         [o,o,o,o,o,o,o,o,o,o,o]]

def continent_size world, x, y
  if world[x][y] != 'land'
    # either it's water or we already counted it,
    # but either way, we don't want to count it now.
    return 0
  end
  # so first we count this tile...
  size = 1
  world[x][y] = 'counted land'
  #...then we count all of the neighboring eight tiles
  # (and, of course, their neighbors by way of the recursion).
  size = size + continent_size(world, x-1, y-1)
  size = size + continent_size(world, x  , y-1)
  size = size + continent_size(world, x+1, y-1)
  size = size + continent_size(world, x-1, y  )
  size = size + continent_size(world, x+1, y  )
  size = size + continent_size(world, x-1, y+1)
  size = size + continent_size(world, x  , y+1)
  size = size + continent_size(world, x+1, y+1)
  size
end

puts continent_size(world, 5, 5)