week 7: Longest Substring Without Repeating Characters

Author: prograsshopper

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

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+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        # sol 1
+        # time complexity: O(n^2) / memory complexity: O(n)
+        if len(s) in [0, 1]:
+            return len(s)
+
+        from collections import defaultdict
+        strings = []
+        for i in range(0, len(s) - 1):
+            char_dict = defaultdict(int)
+            char_dict[s[i]] += 1
+            for j in range(i + 1, len(s)):
+                char_dict[s[j]] += 1
+                if char_dict[s[j]] > 1:
+                    strings.append(s[i:j])
+                    break
+            else:
+                strings.append(s[i:])
+
+        max_len = len(strings[0])
+        for elem in strings:
+            max_len = max(max_len, len(elem))
+        return max_len
+
+        # sol 2
+        # time complexity: O(n) / memory complexity: O(n)
+        str_set = set()
+        left = 0
+        max_len = 0
+
+        for right in range(len(s)):
+            while s[right] in str_set:
+                str_set.remove(s[left])
+                left += 1
+            str_set.add(s[right])
+            max_len = max(max_len, right - left + 1)
+        return max_len