dijkstra shortest path in ruby

shortest_path_spec.rb

require 'spec_helper'

SP = ->(graph, from_node, to_node, nodes = Hash.new(0), visited = [], i = 0) {
  return nodes[from_node] if from_node == to_node

  neighbours = graph[from_node].reject {|k, v| visited.include?(k) }

  neighbours.each do |k, v|
    if nodes[k] == 0 || nodes[from_node] + v < nodes[k]
      nodes[k] = nodes[from_node] + v
    end
  end

  smallest_node = neighbours.sort_by {|k, v| nodes[k]}.first.first
  visited << from_node

  raise 'Loooppppiiing' if i > 7
  SP.(graph, smallest_node, to_node, nodes, visited, i + 1)
}


describe SP do
  let(:graph) do
    {
      '1' => {
        '2' => 7,
        '3' => 9,
        '6' => 14
      },
      '2' => {
        '1' => 7,
        '3' => 10,
        '4' => 15
      },
      '3' => {
        '1' => 9,
        '2' => 10,
        '6' => 2,
        '4' => 11
      },
      '4' => {
        '2' => 15,
        '3' => 11,
        '5' => 6,
      },
      '5' => {
        '4' => 4,
        '6' => 9,
      },
      '6' => {
        '1' => 14,
        '3' => 2,
        '5' => 9,
      }
    }
  end

  it '1 to 1' do
    expect(SP.(graph, '1', '1')).to eq 0
  end

  it '1 to 2' do
    expect(SP.(graph, '1', '2')).to eq 7
  end

  it '1 to 6' do
    expect(SP.(graph, '1', '6')).to eq 11
  end

  it '1 to 5' do
    expect(SP.(graph, '1', '5')).to eq 20
  end

end