Add longest substring

[Chiefpatwal]

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.07%. Comparing base (135fb08) to head (3ed19a4).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6007      +/-   ##
============================================
+ Coverage     69.05%   69.07%   +0.01%     
- Complexity     4663     4666       +3     
============================================
  Files           623      624       +1     
  Lines         17156    17166      +10     
  Branches       3309     3311       +2     
============================================
+ Hits          11847    11857      +10     
  Misses         4855     4855              
  Partials        454      454              

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[Chiefpatwal]

Longest Substring Without Repeating Characters

This implementation utilizes the sliding window technique to efficiently find the length of the longest substring without repeating characters. The algorithm maintains a dynamic window that expands and contracts based on character uniqueness, ensuring optimal performance with a time complexity of O(n). This solution enhances our algorithm collection by addressing common string manipulation challenges, providing an essential tool for developers working with text processing.