お題は「100日後に退職する47歳」 78日目: https://twitter.com/tome_ura/status/1443411147881783300

combi_abx

def combi_abx a,b,x
  print "combi_abx(a:#{a}, b:#{b}, x:#{x})\t"
  x100 = x / 100
  a100 = a
  b100 = b / 10
  b100 = [b100 - 1, 0].max if (b % 10) < (x / 10) % 10
  return 0 if a100 + b100 < x100
  [b100, x100].min + ((a100 < x100) ? 0 : 1)
end

puts " => #{combi_abx(9,0,1000)}"     # => 0
puts " => #{combi_abx(9,9,1000)}"     # => 0
puts " => #{combi_abx(9,10,1000)}"    # => 1
puts " => #{combi_abx(10,0,1000)}"    # => 1
puts " => #{combi_abx(10,30,1000)}"   # => 4
puts " => #{combi_abx(10,36,1050)}"   # => 4
puts " => #{combi_abx(10,35,1050)}"   # => 4
puts " => #{combi_abx(10,34,1050)}"   # => 3
puts " => #{combi_abx(100,50,120)}"   # => 2
puts " => #{combi_abx(100,50,1230)}"  # => 5
puts " => #{combi_abx(100,50,1200)}"  # => 6