Group Anagrams

Python data engineering interview problem. Difficulty: beginner. Pattern: Hashing. About 10 minutes. Free to practice.

Group strings that are anagrams; sort groups and group order. Treat this as a production helper: match the contracted return shape, including empty and duplicate inputs.

Anagrams are words made of the same letters in a different order. 'eat', 'tea' and 'ate' are anagrams of each other. Search tools group such words together. Write a function group_anagrams(strs) that takes a list of words and groups the words that are anagrams of each other. Return a list of groups, where each group is a list of words. To make the output predictable, sort the words inside every group from A to Z, and then sort the groups by their first word. For ['eat', 'tea', 'tan', 'ate', 'nat', 'bat'] the answer is [['ate', 'eat', 'tea'], ['bat'], ['nat', 'tan']]. Keep the print lines in the editor.

Requirements

• Put words with exactly the same letters into the same group.
• A word with no anagram partner forms a group on its own.
• Sort the words inside each group alphabetically.
• Sort the groups by the first word of each group.

Constraints

• Words are lowercase letters.
• Return a list of lists of words.
• Every input word appears in exactly one group.

Examples

Input: group_anagrams(['eat','tea','tan','ate','nat','bat']) Output: [['ate', 'eat', 'tea'], ['bat'], ['nat', 'tan']] Groups keyed by sorted letters.

Topics: lakebench, python, anagram, grouping.

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