320. Generalized Abbreviation

 1     public List<String> generateAbbreviations(String word) {
 2         List<String> res = new ArrayList<String>();
 3         if(word == null) {
 4             return res;
 5         }
 6         generate(res, word, 0, "", 0);
 7         return res;
 8     }
 9     
10     private void generate(List<String> res, String word, int index, String cur, int cnt) {
11         if(index == word.length()) {
12             res.add(cur + ((cnt == 0)?"":cnt));
13             return;
14         }
15         generate(res, word, index + 1, cur, cnt + 1);
16         generate(res, word, index + 1, cur + ((cnt == 0)?"":cnt) + word.charAt(index) , 0);
17     }