ruby - 打印 BFS 中的每个级别

Question

所以，我可以遍历列表，但我无法打印出每一层。不确定如何。

我有这样的东西:

$list = {
  "A" => ["C","D","E"],
  "B" => ["C","F"],
  "C" => ["A","B","D","F","E"],
  "D" => ["A","C","E"],
  "E" => ["A","C","D"],
  "F" => ["B","C"]
 }


def BFS2()
  queue = ["A"]
  visited = {"A"=>true}
  print "A "
    while(!queue.empty?)
      node = queue.pop()
      $list[node].each do |child|
        if visited[child] != true then
           print "#{child} "
           queue.push(child)
           visited[child] = true
         end
      end
    end
end

而不是打印出来

A C D E B F

我喜欢这样打印

A
C D E
B F

我尝试了一些不同的东西，但我似乎无法理解。任何帮助将不胜感激。

Answer 1

该解决方案需要检查您是否真的为给定节点打印了一些内容，这样我们就不会为不应该打印任何内容的节点添加额外的 \n。

解决方案

我们根据需要添加适当的\n。

def BFS2()
  queue = ["A"]
  visited = {"A"=>true}
  puts "A "
    while(!queue.empty?)
      do_print = false
      node = queue.pop()
      $list[node].each do |child|
        if visited[child] != true then
           print "#{child} "
           queue.push(child)
           visited[child] = true
           do_print = true
        end
      end
      if do_print == true
        print "\n "
      end
    end
end