DailyProgrammer Challenge #213i Solution (The Lazy Typist)

c-typist.rb

class Keyboard
  def initialize(rows)
    @keys, @spaces, @shifts = {}, [], []
    rows.each.with_index do |row, j|
      row.each_char.with_index do |c, i|
        unless c == '.'
          @keys[c] = [] unless @keys[c]
          @keys[c] << [i, j]
        end
      end
    end
  end

  def closest(key, px, py)
    @keys[key].sort_by {|(sx, sy)| (sx - px).abs + (sy - py).abs }.first
  end
end

class Hand
  attr_reader :effort, :keyboard, :name, :key
  
  def initialize(keyboard, name, key)
    @keyboard, @name = keyboard, name
    @effort = 0
    @key, @px, @py = key, *@keyboard.closest(key, 0, 0)
  end

  def effort_for(key)
    kx, ky = @keyboard.closest(key, @px, @py)
    (kx - @px).abs + (ky - @py).abs
  end

  def move_to(key)
    kx, ky = @keyboard.closest(key, @px, @py)
    de = (kx - @px).abs + (ky - @py).abs
    @effort += de
    @px, @py = kx, ky
    @key = key
    de
  end
end

$kb = Keyboard.new(['qwertyuiop', 'asdfghjkl', '^zxcvbnm.^', '...     '])
input = gets.chomp
hands, $available_hands = [], ['left', 'right']

def key_to_s(key)
  {' ' => 'Space', '^' => 'Shift'}[key] || key.upcase
end

def move_to(hands, key, but_not=nil)
  if $available_hands.empty?
    possible_hands = but_not ? hands.reject {|hand| hand == but_not } : hands
    possible_hands = hands if possible_hands.empty?
    best_hand = possible_hands.min_by {|hand| hand.effort_for(key.downcase) }
    if best_hand.key == key.downcase
      puts "#{key_to_s(key)}: Use #{best_hand.name} hand again"
    else
      msg = "#{key_to_s(key)}: Move #{best_hand.name} hand from #{key_to_s(best_hand.key)}"
      de = best_hand.move_to(key.downcase)
      msg += " (effort: #{de})"
      puts msg
      best_hand
    end
  else
    name = $available_hands.shift
    puts "#{key_to_s(key)}: Use #{name} hand"
    hands << Hand.new($kb, name, key.downcase)
  end
end

input.each_char do |char|
  (puts "Invalid character in input."; exit) unless char =~ /[A-Za-z ]/
end

while c = input.slice!(0)
  if c =~ /[A-Z]/
    used_hand = move_to(hands, '^')
  else
    used_hand = nil
  end
  used_hand = move_to(hands, c, used_hand)
end

puts "Total effort: #{hands.map {|hand| hand.effort }.reduce(0, :+)}"