[NeetCode 150] Longest Substring Without Duplicates

Longest Substring Without Duplicates

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

A substring is a contiguous sequence of characters within a string.

Example 1:

Input: s = "zxyzxyz"

Output: 3

Explanation: The string “xyz” is the longest without duplicate characters.

Example 2:

Input: s = "xxxx"

Output: 1

Constraints:

0 <= s.length <= 1000

s may consist of printable ASCII characters.

Solution

A typical sliding window problem, a set can be applied to the statistics of appeared characters, because a character can only appears at most once.

Code

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        le = 0
        ans = 0
        char_set = set()
        for ri in range(len(s)):
            while s[ri] in char_set:
                char_set.remove(s[le])
                le += 1
            char_set.add(s[ri])
            ans = max(ans, ri-le+1)
        return ans