length_of_longest_substring.rb

# @param {String} s
# @return {Integer}
def length_of_longest_substring(s)
  chars = s.split('')
  longest = 0
  base = 0

  char_set = Set.new

  (base...chars.length).each do |iter|
    while char_set.include?(chars[iter])
      # move base up and until the dup char is found
      # this acts as a sliding window
      char_set.delete(chars[base])
      base += 1
    end

    # increment longest only when no dup
    len = iter - base + 1
    longest = len if len > longest

    char_set.add(chars[iter])
  end

  longest
end

# expected 3
puts length_of_longest_substring('abcabcbb').inspect
# expected 3
puts length_of_longest_substring('pwwkew').inspect
# same chars, epxected 1
puts length_of_longest_substring('bbb').inspect
# longest in the end, expected 9
puts length_of_longest_substring('pdxdsprlong').inspect
# longest in the front, expected 9
puts length_of_longest_substring('sprlongdxd').inspect