add solution: longest-substring-without-repeating-characters

Author: dusunax

longest-substring-without-repeating-characters/dusunax.py

@@ -0,0 +1,35 @@
+'''
+# 3. Longest Substring Without Repeating Characters
+
+use a set to store the characters in the current substring.
+
+
+## Time and Space Complexity
+
+```
+TC: O(n)
+SC: O(n)
+```
+
+#### TC is O(n):
+- iterating with end pointer through the string once. = O(n)
+- inner while loop runs at most once for each character in the string. = Amortized O(1)
+
+#### SC is O(n):
+- using a set to store the characters in the current substring. = O(n)
+
+'''
+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        max_count = 0
+        start = 0
+        substrings = set() # SC: O(n)
+
+        for end in range(len(s)): # TC: O(n)
+            while s[end] in substrings: # TC: Amortized O(1)
+                substrings.remove(s[start])
+                start += 1
+            substrings.add(s[end])
+            max_count = max(max_count, end - start + 1)
+        
+        return max_count