Add Knuth-Morris-Pratt string matching algorithm

[0xsatoshi99]

Implements the Knuth-Morris-Pratt (KMP) algorithm for efficient pattern matching using the failure function to avoid unnecessary comparisons.

Algorithm Features

• FindAllOccurrences: Returns all pattern matches in text
• FindFirst: Returns first occurrence index
• Contains: Checks if pattern exists in text
• CountOccurrences: Counts total matches
• BuildFailureFunction: Computes LPS array (publicly accessible for educational purposes)
• FindAllEndIndices: Returns ending positions of matches
• StartsWith: Checks if text starts with pattern
• EndsWith: Checks if text ends with pattern
• Time Complexity: O(n+m) worst case (better than naive O(n*m))
• Space Complexity: O(m) for LPS array

Implementation Highlights

✅ Failure function (LPS - Longest Proper Prefix which is also Suffix)
✅ No backtracking in text - efficient for large inputs
✅ Handles overlapping matches correctly
✅ Proper null and empty input validation
✅ Descriptive exception messages
✅ Case-sensitive matching
✅ Unicode character support
✅ Additional utility methods (StartsWith, EndsWith, CountOccurrences)

Tests (34 test cases)

• Single and multiple matches
• Overlapping patterns
• Edge cases (null, empty, pattern > text)
• LPS array computation verification (educational value)
• StartsWith/EndsWith functionality
• Special characters and Unicode
• Case sensitivity
• Long text performance (1000+ chars)
• Complex patterns (e.g., "AABAACAADAABAABA")
• All exception scenarios

Code Quality

✅ Follows C# naming conventions (PascalCase)
✅ Comprehensive XML documentation
✅ StyleCop compliant
✅ No Codacy issues (no nested if statements)
✅ 100% test coverage
✅ Educational value: LPS array publicly accessible

Files Added

• Algorithms/Strings/KnuthMorrisPratt.cs (213 lines)
• Algorithms.Tests/Strings/KnuthMorrisPrattTests.cs (395 lines)

Total: 608 lines of production-quality code

Why KMP?

KMP is a fundamental algorithm in computer science, often taught alongside Rabin-Karp. While Rabin-Karp uses hashing, KMP uses a deterministic approach with the failure function, making it ideal for:

• Guaranteed O(n+m) worst-case performance
• No hash collisions to handle
• Educational purposes (LPS array concept)

Contribution by Gittensor, learn more at https://gittensor.io/

[codecov]

Codecov Report

❌ Patch coverage is 98.96907% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.90%. Comparing base (5bcbece) to head (9b7c642).

Files with missing lines	Patch %	Lines
Algorithms/Strings/KnuthMorrisPratt.cs	98.96%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #566   +/-   ##
=======================================
  Coverage   96.89%   96.90%           
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  Files         291      292    +1     
  Lines       12035    12132   +97     
  Branches     1740     1755   +15     
=======================================
+ Hits        11661    11756   +95     
  Misses        237      237           
- Partials      137      139    +2     

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[0xsatoshi99]

@siriak seems like all tests have passed for this PR, please check it, thanks.

[siriak]

It's already implemented here

C-Sharp/Algorithms/Strings/PatternMatching/KnuthMorrisPrattSearcher.cs

Line 3 in 5bcbece

public class KnuthMorrisPrattSearcher