Find Number of Islands

island_count.rb

require 'set'
# @param {Character[][]} grid
# @return {Integer}
def num_islands(grid)
    puts grid.inspect
    final_count = 0
    grid.length.times do |i|
        grid.length.times do |j|
            matter = grid[i][j]
            if land?(matter) && !surrounding_set(grid, i, j).member? '1'
                final_count += 1
            end
        end
    end
    final_count
end

def land?(matter)
    matter == '1'
end

def surrounding_set(a, i, j)
    set = Set.new
    set.add a.fetch [i-1][j], '0' #Top
    set.add a.fetch [i+1][j], '0' #Bottom
    set.add a.fetch [i][j+1], '0' #Right
    set.add a.fetch [i+1][j], '0' #Left
    set
end

num_islands %w(%w(1 0 0) %w(1 0 0) %w(1 0 1))