Find the Longest Substring Without Repeated Characters

Problem Statement

Given a string s consisting of printable ASCII characters, return the length of the longest contiguous substring that contains no duplicate characters.

Characters are case-sensitive (e.g., 'a' and 'A' are considered distinct characters).

Function Signature

def length_of_longest_substring(s: str) -> int:
    pass

Input & Output

• Input: A single string s of length n containing standard ASCII characters.
• Output: An integer representing the length of the longest substring with all unique characters.

Constraints

• 0 <= len(s) <= 10^5
• s consists of English letters, digits, symbols, and spaces.
• Time complexity must be O(n) to pass within execution time limits.
• Auxiliary space complexity should be O(min(n, m)) where m is the size of the character set (at most 128 for standard ASCII).

Examples

Example 1

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with a length of 3.

Example 2

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with a length of 1.

Example 3

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with a length of 3. Note that "pwke" is a subsequence, not a contiguous substring.

Edge Cases to Consider

• An empty string "" should return 0.
• A string where all characters are identical (e.g., "aaaa") should return 1.
• A string where all characters are already unique should return len(s).
• Strings with spaces or non-alphanumeric ASCII characters (e.g., "a b!c a").