CSV cordinate to index

code2index.rb

require 'pry' 
CODES = ('A'..'Z')
CODES_SIZE = CODES.to_a.size

def index2code(n)
  num = n
  chars = []
  codes = CODES.to_a

  begin
    num -= 1 unless n == num
    chars << codes[num % CODES_SIZE]
    num = num / CODES_SIZE
  end while num > 0

  chars.reverse.join
end

def code2index(code)
  chars = code.split('')
  num = 0
  chars.each.with_index do |c, i|
    n = c.ord - CODES.first.ord
    n += 1 if i < code.length - 1
    num = num * CODES_SIZE + n
  end
  num
end

def testc2i(cord)
  puts "#{cord}:\t#{code2index(cord)}"
end

def testi2c(num)
  puts "#{num}:\t#{index2code(num)}"
end

testi2c 0
testi2c 1
testi2c 2
testi2c 25
testi2c 26
testi2c 27
testi2c 52
testi2c 77
testi2c 700
testi2c 701
testi2c 475253

puts '-' * 12

testc2i 'A'
testc2i 'B'
testc2i 'Z'
testc2i 'AA'
testc2i 'AB'
testc2i 'AZ'
testc2i 'BA'
testc2i 'BB'
testc2i 'BZ'
testc2i 'CA'
testc2i 'ZA'
testc2i 'ZY'
testc2i 'ZZ'
testc2i 'Z' * 3
testc2i 'Z' * 4
testc2i 'Z' * 5