Group Anagrams Together

Problem

Given an array of strings, group all anagrams together. Return groups in any order.

Example

Input: ["eat","tea","tan","ate","nat","bat"]
Output: [["eat","tea","ate"],["tan","nat"],["bat"]]

Constraints

• 1 ≤ strs.length ≤ 10^4
• 0 ≤ strs[i].length ≤ 100
• Strings consist of lowercase English letters

Approach

Use a sorted string (or character frequency tuple) as the hashmap key. O(n·k·log k) where k is max string length.

Follow-up

Can you solve it in O(n·k) using a character count key instead of sorting?