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 * 10^4
s consists of English letters, digits, symbols and spaces.

Solution

Approach

Using sliding window to keep track substrings represent by hash table

def longestPalindrome(s: str) -> str:

        start_index = 0
        chars_map = {}
        max_length = 1

        for i in range(len(s)):

            char = s[i]
            used_char_index = chars_map.get(char, -1)
            if used_char_index >= start_index:
                start_index = used_char_index + 1

            chars_map[char] = i
            max_length = max(max_length, (i + 1) - start_index)

        return max_length


print(longestPalindrome("babad"))  # Output: 2
print(longestPalindrome("abcabcbb")) # Output: 3
print(longestPalindrome("bbbbb")) # Output: 1
print(longestPalindrome(" ")) # Output: 1
print(longestPalindrome("")) # Output: 0
print(longestPalindrome("au")) # Output: 2

Complexity

Time complexity: O(n)
Space complexity: O(n)