ram-ai-kumar · November 12, 2023 09:11 · Nov 12, 2023 · Nov 12, 2023
diff --git a/leetcode_3.rb b/leetcode_3.rb
@@ -20,6 +20,20 @@
 # 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?

diff --git a/leetcode_3.rb b/leetcode_3.rb
@@ -0,0 +1,50 @@
+# [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.
+# 
+
+# 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
No results found