def feed(input)
      heads = [@start]
      
      # Move any initial e-transitions
      if has_transition?(@start, '&')
        transition(@start, '&').each { |h| heads << h } 
      end
      
      # Iterate through each symbol of input string
      input.each_char do |symbol|
        newHeads, eTrans = [], []
                
        heads.each do |head|
          # Check if head can transition read symbol
          # Head dies if no transition for symbol
          if has_transition?(head, symbol)
            transition(head, symbol).each { |t| newHeads << t }
          end
        end
        
        # Move any e-transitions
        newHeads.each do |head|
          if has_transition?(head, '&')
            transition(head, '&').each { |t| eTrans << t }
          end
        end
        eTrans.each { |t| newHeads << t }
        
        heads = newHeads
        break if heads.empty?
      end
      
      accept = false
      heads.each { |head| accept = true if accept_state? head }

      resp = {
        input: input,
        accept: accept,
        heads: heads
      }
    end
def feed(input)
      heads = [@start]
      
      # Move any initial e-transitions
      if has_transition?(@start, '&')
        transition(@start, '&').each { |h| heads << h } 
      end
      
      # Iterate through each symbol of input string
      input.each_char do |symbol|
        newHeads, eTrans = [], []
                
        heads.each do |head|
          # Check if head can transition read symbol
          # Head dies if no transition for symbol
          if has_transition?(head, symbol)
            transition(head, symbol).each { |t| newHeads << t }
          end
        end
        
        # Move any e-transitions
        newHeads.each do |head|
          if has_transition?(head, '&')
            transition(head, '&').each { |t| eTrans << t }
          end
        end
        eTrans.each { |t| newHeads << t }
        
        heads = newHeads
        break if heads.empty?
      end
      
      accept = false
      heads.each { |head| accept = true if accept_state? head }

      resp = {
        input: input,
        accept: accept,
        heads: heads
      }
    end
@todo Check that each state is connected.
   Iterate through each states to verify the graph
   is not disjoint.
 Runs the input on the machine and returns a Hash describing
 the machine's final state after running.

 @param [String] input the string to use as input for the NFA
 @return [Hash] a hash describing the NFA state after running
   * :input [String] the original input string
   * :accept [Boolean] whether or not the NFA accepted the string
   * :heads [Array] the state which the head is currently on