Ruby - CountingDuplicates.txt

Write a function that will return the count of distinct case-insensitive alphabetic characters that occur more than once in the given string. The given string can be assumed to contain only uppercase and lowercase alphabets.


- - - - - - - my answer - - - - - - -


def duplicate_count(text)
    uniChars, total = {}, 0
    text.downcase.chars.map { |char| uniChars.has_key?(char) ? uniChars[char] += 1 : uniChars[char] = 1 }
    uniChars.values.map { |occurance| occurance > 1 ? total+=1 : nil }
    total
end


- initialize an empty hash and a counter
- take input text, downcast it, split it and iterate over each char
  - if the char doesn’t exists in the hash, add it with an ‘occurrence’ of 1
  - if the char does exist, increment the occurrence up one.
- look at each the values stored in the uniChars hash
  - if the value is greater than 1 increment the ‘total’ up by 1
-return total


- - - alt - - -

def duplicate_count(text)
  ('a'..'z').count { |c| text.downcase.count(c) > 1 }
end

- this answer starts by creating a range of characters
- they then may over each char of the alphabet comparing it to the (downcased) letters supplied in ‘text’

- - - alt - - -

def duplicate_count(text)
   text
    .downcase
    .chars
    .sort
    .chunk { |c| c }
    .count { |_, occurrences| occurrences.count > 1 }

- oh my god. ‘.chunk’ is super interesting.
  - it groups like elements in an array together
    - in this challenge they sort characters together and then ‘chunk’ them together.
- i don’t fully understand the last line, but they’re doing something similar to what I did above looking for occurrences above 1