03. Longest Substring Without Repeating Characters.py

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        charSet=set()
        l=0

        res=0
        for r in range(len(s)):
            while s[r] in charSet:
                charSet.remove(s[l])
                l+=1
            charSet.add(s[r])
            res= max(res,r-l + 1)
        return res