CODEWITHSUNDEEP
rubystring
user3760731
user3760731

Reputation:

Ruby converting letters in string to letters 13 places further in the alphabet

I'm trying to solve a problem where when given a string I convert each letter 13 places further in the alphabet. For example

a => n
b => o
c => p

Basically every letter in the string is converted 13 alphabet spaces.

If given the string 'sentence' i'd like it to convert to

'feagrapr'

I have no idea how to do it. I've tried

'sentence'.each_char.select{|x| 13.times{x.next}}

and I still couldn't solve it.

This one has been puzzling me for a while now, and I've given up trying to solve it.

I need your help

Upvotes: 1

Views: 1181

Answers (3)

O-I
O-I

Reputation: 1575

Using String#tr as TCSGrad suggests is the ideal solution.

Some alternatives:

Using case, ord, and chr

word = 'sentence'

word.gsub(/./) do |c|
  case c
  when 'a'..'m', 'A'..'M' then (c.ord + 13).chr
  when 'n'..'z', 'N'..'Z' then (c.ord - 13).chr
  else c
  end
end

Using gsub and a hash for multiple replacement

word = 'sentence'
from = [*'a'..'z', *'A'..'Z']
to = [*'n'..'z', *'a'..'m', *'N'..'Z', *'A'..'M']
cipher = from.zip(to).to_h

word.gsub(/[a-zA-Z]/, cipher)

Note, Array#to_h requires Ruby 2.1+. For older versions of Ruby, use

cipher = Hash[from.zip(to)].

Upvotes: 1

TCSGrad
TCSGrad

Reputation: 12118

IMHO, there is a better way to achieve the same in idiomatic Ruby:

def rot13(string)
  string.tr("A-Za-z", "N-ZA-Mn-za-m")
end

This works because the parameter 13 is hard-coded in the OP's question, in which case the tr function seems to be just the right tool for the job!

Upvotes: 4

Afonso Tsukamoto
Afonso Tsukamoto

Reputation: 1214

From here -> How do I increment/decrement a character in Ruby for all possible values?

you should do it like: 

def increment_char(char)
 return 'a' if char == 'z'
 char.ord.next.chr
end

def increment_by_13(str)
 conc = []
 tmp = ''
 str.split('').each do |c|
   tmp = c
   13.times.map{ |i| tmp = increment_char(tmp) }
   conc << tmp
 end
 conc
end

Or close.

Upvotes: -1

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