simple bfs

gistfile1.rb

for cell in map do
  cell.visited = false
end

biome_search_type = 'lake'
contiguous_cells = []

queue = [start_cell]
start_cell.visited = true

while queue.length > 0
  cell = queue.shift
  if cell.type == biome_search_type
    contiguous_cells.push(cell)
    for neighbour_cell in cell.neighbours
      unless neighbour_cell.visited
        neighbour_cell.visited = true
        queue.push(neighbour_cell)
      end
    end
  end
end

# `contiguous_cells` contains all neighbour cells with the desired biome type