deserialzer.rb

def deserialize(input)
  h = {}
  l = 0
  stack = []
  curr_string = ""
  while l < input.length do
    case input[l]
    when "{" #state = DICT_START
      curr_string = ""
    when ":" #state =  VALUE_START
      stack.push(curr_string)
      curr_string = ""
    when "}", "," #state = DICT_END
      if curr_string != "" then
        stack.push(curr_string)
      end
      if stack.length > 0 then
        val = stack.pop
        key = stack.pop
        stack.push({key => val})
      end  
      curr_string = ""
    else
      curr_string+=input[l]
    end
    l+=1
  end
  stack.each {|n| h.merge!(n)}
  h
end

p deserialize("{a:test,b:test1,c:test3}")
p deserialize("{a:{b:test1}}")
p deserialize("{a:{b:{c:test1}}}")
p deserialize("{a:{b:{c:test1}},d:123}")

Input: "{a:test,b:test1,c:test3}" #string
Output: {"a"=>"test", "b"=>"test1", "c"=>"test3"} #hash nested to any level
Input: "{a:{b:test1}}"
Output: {"a"=>{"b"=>"test1"}}
Input: "{a:{b:{c:test1}}}"
Output: {"a"=>{"b"=>{"c"=>"test1"}}} #hash nested to any level
Input: "{a:{b:{c:test1}},d:123}"
Output: {"a"=>{"b"=>{"c"=>"test1"}}, "d"=>"123"}