49. Group Anagrams

Given an array of strings, group anagrams together.
Example:

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

Note:
All inputs will be in lowercase.
The order of your output does not matter.

难度：medium

题目：给定一个字符串数组，将 颠倒字母而成的单词 组合在一起。
注意：所有输入都为小写字母

思路：都按字母序排序。

Runtime: 14 ms, faster than 85.30% of Java online submissions for Group Anagrams.
Memory Usage: 34.1 MB, less than 16.58% of Java online submissions for Group Anagrams.

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        Map<String, List<String>> msl = new HashMap<>();
        
        for (int i = 0; i < strs.length; i++) {
            char[] sc = strs[i].toCharArray();
            Arrays.sort(sc);
            String ns = new String(sc);
            msl.putIfAbsent(ns, new ArrayList<String>());
            msl.get(ns).add(strs[i]);
        }
        
        return new ArrayList(msl.values());
    }
}