groupanagrams-sort.java

    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>> res = new ArrayList<>();

        if (strs == null || strs.length == 0) {
            return res;
        }

        Map<String, List<String>> lookup = new HashMap<>();

        for (String s : strs) {
            String sortedStr = this.sortString(s);
            if (lookup.containsKey(sortedStr)) {
                lookup.get(sortedStr).add(s);
            } else {
                List<String> list = new ArrayList<>();
                list.add(s);
                lookup.put(sortedStr, list);
            }
        }

        for (Map.Entry<String, List<String>> entry : lookup.entrySet()) {
            List<String> l = entry.getValue();
            Collections.sort(l);
            res.add(l);
        }

        return res;
    }

	private String sortString(String s) {
		char[] a = s.toCharArray();
		Arrays.sort(a);
		// Need to create a new instance
		return new String(a);
	}