3. Longest Substring Without Repeating Characters

MediumStringSliding WindowHash SetTimeO(n)SpaceO(min(n, k))
longest so far: 0
a0
b1
c2
b3
LR
seen{∅}
window 0..0
right → 0 (char 'a')expand
Frame 1 / 20
1class Solution:
2    def lengthOfLongestSubstring(self, s):
3        longest = 0
4        left = 0
5        seen = set()
6        for right in range(len(s)):
7            char = s[right]
8            while char in seen:
9                seen.remove(s[left])
10                left += 1
11            seen.add(char)
12            longest = max(longest, right - left + 1)
13        return longest