Leetcode 3: Longest Substring Without Repeating Characters - Java Solution with visualisation

Certainly, let's break down this Java code, which finds the length of the longest substring without repeating characters in a given string.

*Explanation:*

1. *Initialization:*
- `start`: An integer to track the beginning of the current substring.
- `end`: An integer to track the end of the current substring.
- `maxLength`: An integer to store the length of the longest substring found so far, initially 0.
- `set`: A HashSet to store unique characters encountered in the current substring.

2. *Sliding Window Approach:*
- The code uses a sliding window technique, where the window represents the current substring.
- The `start` and `end` pointers define the boundaries of the window.

3. *Iteration:*
- The `while` loop iterates through the string:
- *Check for Duplicates:*
- If the character at the current `end` position is already present in the `set`, it means we've encountered a duplicate.
- To remove the duplicate, we move the `start` pointer to the right until the duplicate character is removed from the `set`.
- *Expand the Window:*
- If no duplicate is found:
- Add the current character at `end` to the `set`.
- Move the `end` pointer to the right to expand the window.
- Update `maxLength` if the current window size is greater than the previous maximum.

4. *Return the Maximum Length:*
- After the loop, `maxLength` will hold the length of the longest substring without repeating characters.

*Example:*

Let's say the input string is "abcabcbb".

- Initial: `start = 0`, `end = 0`, `set = {}`, `maxLength = 0`
- Iterate:
- `end = 1`, `set = {'a'}`, `maxLength = 1`
- `end = 2`, `set = {'a', 'b'}`, `maxLength = 2`
- `end = 3`, `set = {'a', 'b', 'c'}`, `maxLength = 3`
- `end = 4`, `set = {'b', 'c', 'a'}` (remove 'a' from set and move `start` to 1), `maxLength = 3`
- `end = 5`, `set = {'c', 'a', 'b'}` (remove 'b' from set and move `start` to 2), `maxLength = 3`
- `end = 6`, `set = {'a', 'b', 'c'}` (remove 'c' from set and move `start` to 3), `maxLength = 3`

- Return `maxLength` which is 3.

*Key Points:*

- The sliding window technique efficiently explores all possible substrings.
- The HashSet allows for efficient checking and removal of duplicate characters.
- This solution provides an optimal way to find the longest substring without repeating characters.

I hope this explanation is helpful! Let me know if you have any further questions.

#leetcodejava #leetcode #leetcodesolution #100daysofcode #datastructures #datastructuresandalgorithms #java #programming #coding #tutorial #tutorialvideo #learntocode2024 #codewithme #codingchallenge #techtips #codingcommunity #youtube #youtubetutorial #youtubevideo #algorithms #leetcode #leetcodejava