Find the first un-repeated character in a string

Question

What is the quickest way to find the first character which only appears once in a string?

Answer 1

In Ruby:

(Original Credit: Andrew A. Smith)

x = "a huge string in which some characters repeat"

def first_unique_character(s)
 s.each_char.detect { |c| s.count(c) == 1 }
end

first_unique_character(x)
=> "u"