"Cookpad Daily Ruby Puzzles" in RubyKaigi 2019 - All problems

README.md

Cookpad Daily Ruby Puzzles

The Cookpad booth event in RubyKaigi 2019

See also the extra stage!

Day-1

• puzzle-1-1.rb: authored by @ko1
• puzzle-1-2.rb: authored by @ko1
• puzzle-1-3.rb: authored by @mame

Day-2

• puzzle-2-1.rb: authored by @ko1
• puzzle-2-2.rb: authored by @mame
• puzzle-2-3.rb: authored by @mame

Day-3

• puzzle-3-1.rb: authored by @ko1
• puzzle-3-2.rb: authored by @mame
• puzzle-3-3.rb: authored by @mame

puzzle-1-1.rb

# Hint: Use Ruby 2.6.
puts "#{"Goodbye" .. "Hello"} world"

puzzle-1-2.rb

puts&.then {
  # Hint: &. is a safe
  # navigation operator.
  "Hello world"
}

puzzle-1-3.rb

include Math
# Hint: the most beautiful equation
Out, *,
     Count = $>,
             $<, E ** (2 * PI)
Out.puts("Hello world" *
         Count.abs.round)

puzzle-2-1.rb

def say
  -> {
    "Hello world"
  }
  # Hint: You should call the Proc.
  yield
end

puts say { "Goodbye world" }

puzzle-2-2.rb

e = Enumerator.new do |g|
  # Hint: Enumerator is
  # essentially Fiber.
  yield "Hello world"
end

puts e.next

puzzle-2-3.rb

$s = 0
def say(n = 0)
  $s = $s * 4 + n
end

i, j, k = 1, 2, 3

say i
say j
say k

# Hint: Binary representation.
$s != 35 or puts("Hello world")

puzzle-3-1.rb

def say s="Hello", t:'world'
  "#{ s }#{ t } world"
end
# Hint: Arguments in Ruby are
# difficult.

puts say :p

puzzle-3-2.rb

def say s, t="Goodbye "
  # Hint: You can ignore a warning.
  s = "#{ s } #{ t }"
  t + "world"
end

puts say :Hello

puzzle-3-3.rb

def say
  "Hello world" if
    false && false
  # Hint: No hint!
end

puts say