What is the time and space complexity of Group Anagrams?

Time complexity: O(n * k log k). Space complexity: O(n * k).

Group Anagrams

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Concept

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Solution Guide: Group Anagrams

Approach

For each string, sort its characters to create a canonical key. Use a hash map where the key is the sorted string and the value is a list of original strings sharing that key. Strings that are anagrams of each other produce the same sorted key.

Complexity Analysis

Time: O(n * k log k)
Space: O(n * k)

Pattern

Hash Map Grouping

Why It Works

Anagrams are permutations of the same characters, so sorting them produces an identical string. This sorted form serves as a unique group identifier in the hash map.

Updated Feb 2026