feat: Add Regular Expression Matching algorithm with DP implementation

[kokatesaurabh]

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# Regular Expression Matching

## 📋 Problem Description
This implementation solves the Regular Expression Matching algorithm (LeetCode #10) with support for `'.'` (any single character) and `'*'` (zero or more of preceding element) operators. The solution ensures the entire input string must match the pattern, not just a substring.

## 🚀 Features Implemented
- **Two DP implementations**:
  - Recursive with memoization (top-down)
  - Iterative tabulation (bottom-up)
- **Comprehensive input validation** with meaningful error messages
- **Full pattern validation** ensuring `'*'` always follows valid characters
- **Extensive test coverage** with 40+ test cases

## 🧩 Algorithm Details
- **Time Complexity**: O(m × n) where m = string length, n = pattern length
- **Space Complexity**: O(m × n) for DP table
- **Approach**: Dynamic Programming with state tracking of string and pattern indices

## 📝 Key Features
✅ Handles `'.'` wildcard character  
✅ Handles `'*'` quantifier (zero or more occurrences)  
✅ Validates pattern format and input constraints  
✅ Covers edge cases (empty strings, complex patterns)  
✅ Matches LeetCode problem specifications exactly  

## 🧪 Test Coverage
- Basic exact matching scenarios
- Dot wildcard functionality
- Star quantifier patterns
- Complex pattern combinations
- Edge cases and boundary conditions
- Invalid input validation
- LeetCode example test cases
- Cross-validation between both implementations

## 📁 Files Added

src/main/java/com/thealgorithms/dynamicprogramming/RegularExpressionMatching.java
src/test/java/com/thealgorithms/dynamicprogramming/RegularExpressionMatchingTest.java

## 🔍 Example Usage
```java
// Basic matching
RegularExpressionMatching.isMatch("aa", "a");        // false
RegularExpressionMatching.isMatch("aa", "a*");       // true
RegularExpressionMatching.isMatch("ab", ".*");       // true

// Complex patterns
RegularExpressionMatching.isMatch("aab", "c*a*b");   // true
RegularExpressionMatching.isMatch("mississippi", "mis*is*p*."); // false

📊 Validation

✅ Follows project coding standards and checkstyle
✅ Includes comprehensive JavaDoc documentation
✅ Passes all existing tests in the repository
✅ No breaking changes to existing functionality
✅ Proper error handling and input validation

🎯 Use Cases

• String pattern matching in text processing
• Input validation with complex patterns
• Educational demonstration of dynamic programming
• Foundation for more complex regex implementations

This implementation provides a robust, well-tested solution that follows the project's contribution guidelines and adds value to the algorithms collection.

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Checklist

• My code follows the code style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings