Group Anagrams

Classic LC 49 — bucket strings into anagram groups. Surfaced in a recent Sr SDE phone screen as the warm-up. Requirements Input: List[str] strs. Return groups of strings that are anagrams of each other. Any group ordering is acceptable; group internal order does not matter. Empty string is a valid anagram of itself. Examples Input: ["eat", "tea", "tan", "ate", "nat", "bat"] Output: [["eat","tea","ate"], ["tan","nat"], ["bat"]] Notes Standard pattern: hash by sorted string (O(n·k·log k)) or by 26-length character-count tuple (O(n·k) for lowercase ASCII). For an interviewer who pushes on k being large, the count-tuple variant wins; otherwise either is acceptable. Phone-screen pace: aim for one-pass build + return values in under 10 minutes so the second problem has room. Preparation Write both the sort-key and the tuple-key versions cold; pick the tuple version under time pressure. Practice the follow-up of returning groups sorted by group size descending — adds a single sorted(groups.values(), key=len, reverse=True) step.