find_ocean_recursion.rb

=begin

Given

1. An array of strings where "L" indicates land and "W" indicates water,
2. a coordinate marking a starting point in the middle of the ocean

The Challenge:
Find and mark the ocean in the map by changing appropriate W's to O's.
An ocean coordinate is defined to be any coordinate directly adjacent to any other ocean coordinate.

 Example:
 map = [ "LLLLLLLLWW",
         "LLLLLLLWWW",
         "WWWLLLLLWW" ]

 coordinate: [0,9]

RESULT:

[ "LLLLLLLLOO",
  "LLLLLLLOOO",
  "WWWLLLLLOO" ]

More examples:
map = [ "LLWWWWLLWW",
        "LLWLLWWWWW",
        "WWWLLLLLWW" ]

coordinate: [2,8]

RESULT:

[ "LLOOOOLLOO",
  "LLOLLOOOOO",
  "OOOLLLLLOO" ]

coordinate: [1,2]
Same result.

map = [ "LWWWWLLLWW",
        "WWLLWLLWWW",
        "WWWWWWWWWW" ]

coordinate: [0,9]

RESULT:

[ "LOOOOLLLOO",
  "OOLLOLLOOO",
  "OOOOOOOOOO" ]

=end

# Solution with recursion
def find_ocean(map, x, y)
  if map[x][y] == 'W'
    map[x][y] = 'O'
    adjacent_cells(map, x, y).each do |cell|
      find_ocean map, cell[:x], cell[:y]
    end
  end
end

def adjacent_cells(map, x, y)
  water_cells = []
  water_cells << {x: x - 1, y: y} if x > 0 && map[x - 1][y] == 'W'
  water_cells << {x: x + 1, y: y} if map[x + 1] && map[x + 1][y] == 'W'
  water_cells << {x: x, y: y - 1} if y > 0 && map[x][y - 1] == 'W'
  water_cells << {x: x, y: y + 1} if map[x][y + 1] == 'W'
  water_cells
end

map = [ "LLLLLLLLWW",
        "LLLLLLLWWW",
        "WWWLLLLLWW" ]

find_ocean(map, 0, 9)

map.each{|x| puts x }