Rubyで深さ優先探索

dfs.rb

def solve
  n, m, g = gets.split(' ').map(&:to_i)
  graph = Array.new(n) { Array.new }
  m.times do
    a, b = gets.split(' ').map(&:to_i)
    graph[b - 1] << a - 1
  end

  visited = Array.new(n, false)
  dfs = ->(crt) do
    visited[crt] = true
    graph[crt].each do |nxt|
      dfs.call(nxt) if !visited[nxt]
    end
  end

  dfs.call(g - 1)
  puts visited.all?(true) ? 'OK' : 'NG'
end

solve