My solution for "Cookpad Code Puzzle for RubyKaigi 2022" https://ruby-puzzles-2022.cookpad.tech/

ruby-puzzles-2022.rb

# coding: utf-8
def answer1(n)
  n + 1
end

def answer2(str)
  str.upcase
end

def answer3(n)
  (0..n).to_a
end

def answer4
  x = yield 
  x + 42
end

def answer5(x, *args)
  if args.empty?
    x + 1
  else
    x + args.sum
  end
end

def answer6(n)
  while n >= 10 do
    n = n.to_s.chars.map{|c| c.to_i }.sum
  end
  n
end

def answer7(n)
  n.succ
end

def answer8(n)
  format("%b", n).chars.select{|c| c == '1' }.size
end

def answer9(s)
  s.gsub("u-g0t-me", "yikes")
end

$state10 = 0
def answer10(reset=false)
  if reset
    $state10 = 0
  else
    $state10 += 1
  end
end

# localStorage.stage = 20

def answer11(n)
  n.hash
end

def answer12(n)
  h = Hash.new(0)
  n.to_s.chars.each{|c| h[c] += 1 }
  h.values.inject(1){|a,b| a*b}
end

def answer13(n)
  e = Encoding.list[n]
  if e.nil?
    nil
  else
    e.name[0..1]
  end
end

def answer14(n)
  if n == 1000
    "T"
  elsif n < 20
    "ZOTTFFSSENTETTFFSSEN"[n]
  else
    "ZOTTFFSSEN"[n.to_s[0].to_i]
  end
end

def answer15(n)
  x = Object.constants.map{|x| x.to_s}.sort[n]
  if x.nil?
    x
  else
    x[0..1]
  end
end

def answer16(&blk)
  flag = false
  blk.call { flag = true }
  flag
end

def answer17(s)
  JS.eval("alert(\"#{s}\")")
end

def answer18(s)
  ret = []
  s.scan(/\G\s*(?:(\d+)|([+\-*\/()])|(\z)|(.))/m) {
    if $1
      ret << $1.to_i
    elsif $2
      ret << $2
    elsif $4
      ret << $4
    end      
  }
  ret
end


def parse_expr(ts)
  lhs = parse_term(ts)
  while ts.size > 0 && (ts[0] == '+' || ts[0] == '-')
    op = ts.shift
    rhs = parse_term(ts)
    lhs = [op, lhs, rhs]
  end
  lhs
end

def parse_term(ts)
  lhs = parse_factor(ts)  
  while ts[0] == "*" || ts[0] == "/"
    op = ts.shift
    rhs = parse_factor(ts)
    lhs = [op, lhs, rhs]
  end
  lhs
end

def parse_factor(ts)
  if ts[0] == '('
    ts.shift
    ret = parse_expr(ts)
    ts.shift
    ret
  else
    ["value", ts.shift]
  end
end

def answer19(ts)
  parse_expr(ts)
end

def answer20(e)
  case e
  in ["value", x]
    x
  in ["+", x, y] 
    answer20(x) + answer20(y)
  in ["-", x, y]
    answer20(x) - answer20(y)
  in ["*", x, y]
    answer20(x) * answer20(y)
  in ["/", x, y]
    answer20(x) / answer20(y)
  end
end