49. 字母异位词分组.java

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