Problem

In Meta Messenger, you are given a list of lowercase strings and need to group together strings that are anagrams of each other. Two strings are anagrams if they contain the same characters with the same frequencies, possibly in a different order.

Write a function that returns a list of groups, where each group contains strings from the input that are anagrams of one another. The order of groups does not matter, and the order of strings within each group does not matter.

Formal Specification

• Input: strs, a list of strings
• Output: A list of lists of strings, where each inner list is one anagram group

Examples

Example 1

• Input: strs = ["eat", "tea", "tan", "ate", "nat", "bat"]
• Output: [["eat", "tea", "ate"], ["tan", "nat"], ["bat"]]
• Explanation: Words with the same sorted character sequence belong in the same group.

Example 2

• Input: strs = [""]
• Output: [[""]]
• Explanation: The empty string forms its own anagram group.

Constraints

• 1 <= len(strs) <= 10^4
• 0 <= len(strs[i]) <= 100
• strs[i] contains only lowercase English letters