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3. Longest Substring Without Repeating Characters

Hash Table String Sliding Window

Problem - Longest Substring Without Repeating Characters

Medium

Given a string s, find the length of the longest substring without duplicate 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.

 

Constraints:

  • 0 <= s.length <= 5 * 104
  • s consists of English letters, digits, symbols and spaces.

Solutions

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class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        top = {}
        counter = left = 0

        for right, char in enumerate(s):
            if char in top and top[char] >= left:
                left = top[char] + 1
            top[char] = right
            counter = max(counter, right - left + 1)

        return counter

Submission Stats:

  • Runtime: 11 ms (94.96%)
  • Memory: 17.9 MB (33.90%)