Valid Anagram

Problem
Determine whether two strings are anagrams of each other (same characters with the same frequencies). Then, given a list of strings, group all anagrams together.

Input / Output

• Input: for part one, two strings s and t; for part two, an array of strings.
• Output: part one, a boolean; part two, a list of groups, each group containing mutually-anagram strings.

Constraints

• 1 <= |s| <= 10^5
• Define whether comparison is case-sensitive and the character set (lowercase a-z vs full Unicode).

Example

• "listen", "silent" -> true; "rat", "car" -> false
• group ["eat","tea","tan","ate","nat","bat"] -> [["eat","tea","ate"],["tan","nat"],["bat"]]