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Use a hash map to group strings by a canonical key that is identical for all anagrams, such as the sorted string or a character count signature. Iterate through the input array, compute the key for each string, and append the string to the corresponding group. Finally, return the values of the hash map as a list of lists.
Pro tip: Discuss the trade-offs between sorting each string (O(k log k) per string) and using a character count array (O(k) per string) as the key, and mention that the character count approach can be more efficient for long strings or large alphabets.
Ask clarifying questions about input constraints, such as string length, character set, and whether the output order matters. Confirm that anagrams are case-sensitive and that empty strings are considered anagrams of each other.
Decide on a method to generate a unique key for each anagram group. Common approaches are sorting the string or using a character frequency count. Explain why the key must be identical for all anagrams.
Outline the steps: initialize a hash map, iterate over each string, compute its key, and add the string to the list associated with that key. Mention that the map's values will be the final groups.
State the time and space complexity. For sorting approach: O(n * k log k) time, O(n * k) space. For counting approach: O(n * k) time, O(n * k) space. Discuss trade-offs.
Consider edge cases like empty input, single string, strings with repeated characters, and Unicode characters. Walk through a small example to verify correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.