如何从散列中创建路径？

Question

I am trying to locate the route of the shortest path of a map(connected nodes with weight/distance).

Let's assume I have a hash like this:

{"A"=>{"B"=>1, "E"=>1}, "B"=>{"A"=>1, "C"=>1, "F"=>1}, "C"=>{"B"=>1, "D"=>1, "G"=>1}, "D"=>{"C"=>1, "H"=>1}, "E"=>{"F"=>1, "A"=>1, "I"=>1}, "F"=>{"E"=>1, "G"=>1, "B"=>1, "J"=>1}, "G"=>{"F"=>1, "H"=>1, "C"=>1, "K"=>1}, "H"=>{"G"=>1, "D"=>1, "L"=>1}, "I"=>{"J"=>1, "E"=>1, "M"=>1}, "J"=>{"I"=>1, "K"=>1, "F"=>1, "N"=>1}, "K"=>{"J"=>1, "L"=>1, "G"=>1, "O"=>1}, "L"=>{"K"=>1, "H"=>1, "P"=>1}, "M"=>{"N"=>1, "I"=>1}, "N"=>{"M"=>1, "O"=>1, "J"=>1}, "O"=>{"N"=>1, "P"=>1, "K"=>1}, "P"=>{"O"=>1, "L"=>1}} 

Now I want to traverse and make a path from this hash. For example:

From Source A to Destination: L

Output should be: either A -> E -> I -> J -> K -> L or A -> B -> C -> D -> H -> L .

Here is the function I wrote:

def find_path(src, dst, init = [])
  path = [src]
  neighbors = self.neighbors(src)
  puts "src: #{src}"
  puts "dst: #{dst}"
  # puts "node: #{node}"
  puts "init: #{init}"
  puts "path: #{path}"
  puts "----\n"

  if neighbors.include?(dst)
    path.push(dst)
  else
    path.push(@nodes[src].keys.map{|k| k unless init.flatten.include? k }.reject(&:blank?).each{|key| self.find_path(key, dst, init << path) } )
  end
  return path
end

But, this prints only : ["A", ["B", "E"]]

Which is not the desired output, can anybody tell me how do I go make this work? Thanks.

Update: This was used for locating the route of the shortest path of a map(connected nodes with weight/distance). Here are the details on what I was trying to achieve in this question: https://gist.github.com/suryart/6439102

Answer 1

The original hash:

h = {"A"=>{"B"=>1, "E"=>1}, "B"=>{"A"=>1, "C"=>1, "F"=>1}, "C"=>{"B"=>1, "D"=>1, "G"=>1}, "D"=>{"C"=>1, "H"=>1}, "E"=>{"F"=>1, "A"=>1, "I"=>1}, "F"=>{"E"=>1, "G"=>1, "B"=>1, "J"=>1}, "G"=>{"F"=>1, "H"=>1, "C"=>1, "K"=>1}, "H"=>{"G"=>1, "D"=>1, "L"=>1}, "I"=>{"J"=>1, "E"=>1, "M"=>1}, "J"=>{"I"=>1, "K"=>1, "F"=>1, "N"=>1}, "K"=>{"J"=>1, "L"=>1, "G"=>1, "O"=>1}, "L"=>{"K"=>1, "H"=>1, "P"=>1}, "M"=>{"N"=>1, "I"=>1}, "N"=>{"M"=>1, "O"=>1, "J"=>1}, "O"=>{"N"=>1, "P"=>1, "K"=>1}, "P"=>{"O"=>1, "L"=>1}} 

Converting the original hash since its format sucks:

h.keys.each{|k| h[k] = h[k].keys}
h.default = []

The method:

def find_path h, src, dst
  paths = [[src]]
  loop do
    paths = paths.flat_map do |path|
      h[path.last].map do |nekst|
        a = [*path, nekst]
        a.last == dst ? (return a) : a
      end
    end
  end
end

Trying it:

find_path(h, "A", "L")
# => ["A", "B", "C", "D", "H", "L"]

Notice that if there is no solution, then the loop may run forever. You might want to limit that by adding a limit to the length.