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Yes, Alien Dictionary is a well-known hard graph problem frequently discussed in interviews at companies like Google, Amazon, and Meta. It tests understanding of graphs, topological sorting, and edge-case handling.
The optimal approach models characters as nodes in a directed graph and derives edges from the first differing characters of adjacent words. A topological sort (BFS with Kahn’s Algorithm or DFS with cycle detection) is then used to determine the valid character ordering.
Topological sorting helps determine a valid order of nodes in a directed acyclic graph. Since character dependencies form directed edges, topological order naturally represents the alien alphabet order.
A directed graph represented using an adjacency list works best for this problem. Along with it, an indegree array or map is commonly used for BFS-based topological sorting.