map integer values to chars in array

Question

I've got a method that generates random strings:

def generate_letters(length)
    chars = 'ABCDEFGHJKLMNOPQRSTUVWXYZ'
    letters = ''
    length.times { |i| letters << chars[rand(chars.length)] }
    letters
  end

I want to map values to generated strings, e.g.(1): A = 1, B = 2, C = 3 , e.g.(2): if I generate ACB it equals to 132. Any suggestions?

Sorry, how do you mean 'map'? Do you want to get number 132 base on generated string 'ACB' or you need smth else? — KL-7
– KL-7, Commented Dec 27, 2011 at 16:19
yes - basing on that example, if my method generate 'BAC' string I want to recognize it as 213 — lukaszkups
– lukaszkups, Commented Dec 27, 2011 at 16:22

KL-7 · Accepted Answer · 2011-12-27 17:15:05Z

1

You can use that for concatenating these values:

s = 'ACB'
puts s.chars.map{ |c| c.ord - 'A'.ord + 10 }.join.to_i
# => 101211

and to sum them instead use Enumerable#inject method (see docs, there are some nice examples):

s.chars.inject(0) { |r, c| r + (c.ord - 'A'.ord + 10) } # => 33

or Enumerable#sum if you're doing it inside Rails:

s.chars.sum { |c| c.ord - 'A'.ord + 10 } # => 33

edited Dec 27, 2011 at 17:15

answered Dec 27, 2011 at 16:24

KL-7

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5 Comments

lukaszkups Over a year ago

it works! thanks, but could You describe, what each thing in Your code means? I want to understand it :)

lukaszkups Over a year ago

ok, but wait! it doesn't work for all letters - e.g. K is 11th letter but it equals 1 :/ btw. if You can write that it will start counting from 10 (A = 10, B = 11, ... , Z = 35) it will be awesome!

KL-7 Over a year ago

Sorry, my mistake. What should, for example, KZ be converted to? 2035?

KL-7 Over a year ago

Updated the answer. Is that what you need now?

lukaszkups Over a year ago

nothing - I've found description of methods which You've used, thanks!

polvoazul · Accepted Answer · 2011-12-27 16:43:52Z

1

How would you deal with the ambiguity for leters above 10 (J) ? For example, how would you differentiate between BKC=2113 and BAAC=2113?

Disregarding this problem you can do this:

def string_to_funny_number(str)
    number=''
    str.each_byte{|char_value| number << (1 + char_value - 'A'.ord).to_s}
    return number.to_i
end

This function will generate a correct int by concatenating each letter value (A=1,B=2,...) Beware that this function doesn't sanitize input, as i am assuming you are using it with output from other function.

answered Dec 27, 2011 at 16:43

polvoazul

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1 Comment

lukaszkups Over a year ago

differentiate is not required in my case :) I want to add these numbers - e.g ABC = 1 + 2 + 3, AABA = 1 + 1 + 2 + 1 etc. during this transformation

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