二刷49. Group Anagrams

Medium
用char[]排序后的新string做key来建立hashMap. 最后把每个key的所有value加到List里的list就行

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>> res = new ArrayList<>();
        Map<String, List<String>> map = new HashMap<>();
        for (String str : strs){
            char[] chas = str.toCharArray();
            Arrays.sort(chas);
            String chars = String.valueOf(chas);
            if (!map.containsKey(chars)){
                map.put(chars, new ArrayList<String>());
            }
            map.get(chars).add(str);
        }
        for (String key : map.keySet()){
            Collections.sort(map.get(key));
            res.add(map.get(key));
        }
        return res;
    }
}