[LeetCode]--49. Group Anagrams

Given an array of strings, group anagrams together.

For example, given: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”],
Return:

[
  ["ate", "eat","tea"],
  ["nat","tan"],
  ["bat"]
]

Note: All inputs will be in lower-case.

anagrams：由颠倒字母顺序而构成的字

用一个map来存放，map的key存放字符串按字母表字符排序后的顺序，value存放原本的字符串。

public List<List<String>> groupAnagrams(String[] strs) {
        Map<String, ArrayList<String>> map = new HashMap<String<