[Python] Longest Substring Without Repeating Characters - LeetCode

3. Longest Substring Without Repeating Characters

Longest Substring Without Repeating Characters - LeetCode

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

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Examples

1:

Input: s = "abcabcbb"
Output: 3

Explanation: The answer is "abc", with the length of 3.

 

2:

Input: s = "bbbbb"
Output: 1

Explanation: The answer is "b", with the length of 1.

 

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.

 

4:

Input: s = ""
Output: 0

 

Constraints:

• 0 <= s.length <= 5 * 10^4
• s consists of English letters, digits, symbols and spaces.

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Python solution

Python

Accepted 52ms runtime

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        used = dict()
        max_length = start = 0

        for i, c in enumerate(s):
            if c in used and start <= used.get(c):
                start = used.get(c) + 1
            else:
                max_length = max(max_length, i - start + 1)

            used[c] = i

        return max_length

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