Convert spreadsheet column index into character sequence

问题

How can I the get character sequence, for example "AA" from column index 26?

回答1:

Here's a recursive hash that will handle indexing for you:

index_hash = Hash.new {|hash,key| hash[key] = hash[key - 1].next }.merge({0 => "A"})
index_hash[26] #=> "AA"

The key here is the .next method, which when sent to a string, will return the alphabetically following string, e.g. "CD".next #=> "CE".

Could you clarify your first question?

回答2:

class Numeric
  Alph = ("A".."Z").to_a
  def alph
    s, q = "", self
    (q, r = (q - 1).divmod(26)) && s.prepend(Alph[r]) until q.zero?
    s
  end
end

(26+1).alph #=> "AA"

回答3:

c = "A"
26.times { c = c.next }
c # => "AA"

来源：https://stackoverflow.com/questions/13578555/convert-spreadsheet-column-index-into-character-sequence