解题思路

Map

public List<List<String>> groupAnagrams(String[] strs){
        if(strs.length == 0)
            return new ArrayList<>();
        Map<String,List> ans = new HashMap<>();
        for(String s:strs){
            char[] ca = s.toCharArray();
            Arrays.sort(ca);
            String key = String.valueOf(ca);
            if(!ans.containsKey(key))
                ans.put(key,new ArrayList());
            ans.get(key).add(s);
        }
        return new ArrayList(ans.values());
    }