Ruby 中的序数

Question

我的代码适用于除 11、12 和 13 或以最后两位数字结尾的数字之外的所有内容。

def ordinal()

  n = gets.chomp.to_i
  suffix = n % 10

  if suffix == 1
    return "That's the #{n}st item!"
  elsif suffix == 2
    return "That's the #{n}nd item!"
  elsif suffix == 3
    return "That's the #{n}rd item!" 
  else
    return "That's the #{n}th item!"
  end

end

任何帮助将不胜感激！谢谢。

Answer 1

这是一个特殊情况。在检查 1 位数后缀之前先检查 2 位数后缀。像这样的东西

def ordinal(n)
  ending = case n % 100
           when 11, 12, 13 then 'th'
           else
             case n % 10
             when 1 then 'st'
             when 2 then 'nd'
             when 3 then 'rd'
             else 'th'
             end
           end

  "This is #{n}#{ending} item"
end

ordinal(1) # => "This is 1st item"
ordinal(10) # => "This is 10th item"
ordinal(12) # => "This is 12th item"
ordinal(15) # => "This is 15th item"
ordinal(112) # => "This is 112th item"
ordinal(123) # => "This is 123rd item"