Longest Substring Without Repeating Characters - Python 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.

Example 4:

Input: s = ""
Output: 0

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        n = len(s)
        left,right = 0,0
        max_len = 0
        hashmap = collections.defaultdict()
        while right < n:
            if s[right] in hashmap:
                left = max(hashmap.get(s[right]),left)
            max_len = max(max_len,right-left+1)
            hashmap[s[right]] = right+1
            right = right+1
        return max_len  

TC: O(n) SC: O(n)