25_remove_adjacent_duplicates.rb

# Remove adjacent duplicates

# Sometimes we have input with adjacent duplicates, and we want to remove
# those adjacent duplicates, keeping the original input in order.

# Create a method, which takes a string argument and returns a string
# with duplicate adjacent elements removed, preserving the original
# order of characters and preserving original case. Your algorithm
# should be case sensitive, meaning that "Aa" should not be considered
# duplicate adjacent characters, like "aa" or "AA".  

# *E.g.* remove_adjacent_duplicates("AAaAbbCCCcDDcDA") should return "AaAbCcDcDA"

# *E.g.* remove_adjacent_duplicates("abcABCabcABC") should return exactly the same string: "abcABCabcABC"

def remove_adjacent_duplicates(input)
    characters = input.chars

    i = 0
    while i < characters.length
      if characters[i] == characters[i + 1]
        # Deleting at the current index gets us closer to the final output
        # and has a similar effect to incrementing i
        characters.delete_at(i)
      else
        i += 1
      end
    end

    characters.join("")
end