array_elements_diff.rb

# class Array
#   def token_diff(other)
#     memo = 0 
#     self.each_with_index do |element, index|
#       memo += 1 if other[index] != element
#     end 
#     return memo
#   end
# end

# seemed to be a problem in one spec you provided; also in the method calls

require 'rspec'

class Array
  def token_diff(other)
    matches = (0..self.length).collect {|i| self[i].to_s == (other[i].to_s || nil)}
    matches.find_all {|bool| bool==false}.length
  end
end


[:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]].token_diff([:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]).should == 0
[:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]].token_diff([:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "h"]]]).should == 1

a = [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]
b = [:a, [[:c, "h"], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]]]
a.token_diff(b).should == 1

a = [:a, :b, :c, :d, :e]
b = [:a, :b]
a.token_diff(b).should == 3

a = [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "g"]]]
b = [:a, [[:c, "h"], [:a, [[:b, [:c, "d"], [:c, "e"]], [:f, "i"]]]]]
a.token_diff(b).should == 1 # was 2