Graph Algorithms

• Alien Dictionary Alien Dictionary (LeetCode 269) in Java: topological sort with Kahn's algorithm and DFS cycle detection, plus unique-order and must-precede variants.
• Alien Dictionary, Faster: Primitive Arrays Instead of HashMaps Alien Dictionary in Java, up to 2.6x faster: Kahn's algorithm with primitive arrays instead of HashMaps, with benchmarks and the readability trade-offs.