Leetcode - Longest Substring Without Repeating Characters Solution

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.

Constraints:

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

Solution in Python3

class Solution:
def lengthOfLongestSubstring(self, s: str) -> int:
best = 0
non_unique = -1
seen = {}
for index,char in enumerate(s):
last_seen = seen.get(char, -1)
non_unique = max(non_unique, last_seen)
best = max(index-non_unique, best)
seen[char] = index
return best

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