Longest Substring Without Repeating Characters

This challenge asks you to find the length of the longest substring within a given string that contains no repeating characters. This is a classic string manipulation problem with applications in data compression, pattern recognition, and bioinformatics, where identifying unique sequences is crucial. Your solution should efficiently determine the maximum length of such a substring.

Problem Description

You are given a string s consisting of lowercase English letters. Your task is to find the length of the longest substring of s that contains no repeating characters. A substring is a contiguous sequence of characters within a string.

What needs to be achieved:

Identify all possible substrings of the input string s.
For each substring, check if it contains any repeating characters.
Determine the length of the longest substring found that satisfies the no-repeating-characters condition.
Return this maximum length.

Key Requirements:

The substring must be contiguous (characters must be adjacent in the original string).
The substring must not contain any repeating characters.
The solution should be efficient, especially for longer input strings.

Expected Behavior:

The function should take a string s as input and return an integer representing the length of the longest substring without repeating characters.

Edge Cases to Consider:

Empty string: The longest substring is an empty string, so the length should be 0.
String with all unique characters: The longest substring is the entire string itself.
String with all repeating characters (e.g., "aaaaaa"): The longest substring is a single character, so the length should be 1.
Strings with special characters or numbers (although the problem specifies lowercase English letters, consider how your solution would handle other characters).

Examples

Example 1:

Input: "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3. "bbb" is not a valid answer because the letter 'b' is repeated.

Example 2:

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

Example 3:

Input: "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: ""
Output: 0
Explanation: Empty string, so the longest substring has length 0.

Constraints

The length of the input string s will be between 0 and 50,000 (inclusive).
The input string s will only contain lowercase English letters.
Your solution should ideally have a time complexity of O(n), where n is the length of the string. A brute-force O(n^2) or O(n^3) solution might pass for smaller inputs, but will likely time out for larger ones.
Space complexity should be reasonable (e.g., O(1) or O(n) depending on the approach).

Notes

Consider using a sliding window approach to efficiently track the substring and its characters. A hash map (or dictionary) can be helpful to keep track of the characters within the current window and their last seen positions. Think about how to expand and contract the window to maximize the length of the substring while maintaining the no-repeating-characters constraint. Don't focus on returning the substring itself, only its length.