add new algorithm, data structure and design patter for interview

[codomposer]

Add New Algorithm, Data Structure, and Design Pattern

Summary

This PR adds three new implementations to enhance the interview preparation repository:

• Algorithm: Topological Sort
• Data Structure: Trie (Prefix Tree)
• Design Pattern: Strategy Pattern

Changes

🔢 Algorithm - Topological Sort

• Implemented Kahn's algorithm (BFS-based approach)
• Implemented DFS-based approach
• Includes cycle detection for directed graphs
• Time complexity: O(V + E)
• Use cases: task scheduling, build order, course scheduling, dependency resolution

🌳 Data Structure - Trie

• Complete Trie (prefix tree) implementation
• Operations: insert, search, startsWith, remove
• Time complexity: O(m) for all operations (m = string length)
• Space complexity: O(ALPHABET_SIZE * N * M)
• Applications: string retrieval, autocomplete, word frequency statistics

🎨 Design Pattern - Strategy Pattern

• Abstract strategy interface
• Three concrete strategy implementations (A, B, C)
• Context class for strategy management
• Test code with practical sorting example
• Pattern documentation with advantages and use cases

Documentation Updates

• ✅ Updated README.md (Chinese) with all new implementations
• ✅ Updated README_en.md (English) with all new implementations
• ✅ Added detailed explanations, complexity analysis, and applications
• ✅ Included code examples and test functions

Testing

All implementations include test functions:

• testTopologicalSort()- Tests both algorithms with sample graphs
• testTrie() - Tests insert, search, prefix matching, and deletion
• testStrategyPattern() - Demonstrates strategy switching and practical sorting example

Code Quality

• ✅ Follows existing codebase style and conventions
• ✅ Comprehensive inline comments in Chinese
• ✅ Well-structured and production-ready
• ✅ No breaking changes to existing code

Fixes #12