Longest Substring Without Repeating Characters

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

Input:

abcabcbb

Output:

Reasoning:

We start by examining the input string abcabcbb and looking for substrings without repeating characters
The longest such substrings are abc, bcb, and cab, each having a length of $3$ characters
We can see that there are no longer substrings without repeating characters, as any additional character would result in a repeated character
The final output is therefore $3$ , which is the length of the longest substring without repeating characters