Leetcode #3 (flawed?)

leetcode_3.rb

# [Leetcode #3](https://leetcode.com/problems/longest-substring-without-repeating-characters/) says
# Given a string s, find the length of the longest substring without repeating characters.
#
# Example 1:
#
# Input: s = "abcabcbb"
# Output: 3
# Explanation: The answer is "abc", with the length of 3.
#
# Example 2:
#
# Input: s = "bbbbb"
# Output: 1
# Explanation: The answer is "b", with the length of 1.
# Example 3:
#
# Input: s = "pwwkew"
# Output: 3
# Explanation: The answer is "wke", with the length of 3.
# Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
# 

# Why does it seem flawed?
# Problem statement says "Given a string s, find the length of the longest substring without repeating characters"
#
# Leetcode example 2
# "bbbbb" => "b" # should result in 1, because the first 'b' is non-repeating. The 2nd 'b' is repeating.
#
# Leetcode example 1 = flawed based on example 2
# "abcabcbb" => "abcabcb" # should result in 7, not 3, because (1) "abc" is repeating as a word, not character, so "abcabc" becomes non-repeating. (2) repeating "b" gets counted the first time as non-repeating at least. If "bbbbb" results in 1 by counting the first "b" as non-repeating, then why is it not counted in "abcabcb"?.
#
# Leetcode example 3 = flawed based on example 2
# "pwwkew" => "wkew" # should result in 4, not 3
#
# If example 1 and 3 are correct logic, then the result of example 2 should be ZERO

# The solution
# 
# what is this "gsub(/(.)\1+/, '-\1')" regex logic/magic?
#
# (.) = any character, as a "match"
# \1 = first match
# + = one or more chars = also means entire "substring"
# -\1 = '-' as literal, \1 as first "match"
#
# @param {String} s
# @return {Integer}
def lls(s)
    # generate a potential string for regex match
    (
        # replace repeating chars with '-' as prefix
        s.gsub(/(.)\1+/, '-\1') 
        # just a separator
        +' '+ 
        # replace repeating chars with '-' as suffix
        s.gsub(/(.)\1+/, '\1-')
    )
    # regex scan for words
    .scan(/\w+/)
    # collect all word-lengths
    .collect(&:length)
    # find the max length
    .max
end