Leetcode: Unique Word Abbreviation

An abbreviation of a word follows the form <first letter><number><last letter>. Below are some examples of word abbreviations:

a) it                      --> it    (no abbreviation)

     1
b) d|o|g                   --> d1g

              1    1  1
     1---5----0----5--8
c) i|nternationalizatio|n  --> i18n

              1
     1---5----0
d) l|ocalizatio|n          --> l10n
Assume you have a dictionary and given a word, find whether its abbreviation is unique in the dictionary. A word‘s abbreviation is unique if no other word from the dictionary has the same abbreviation.

Example:
Given dictionary = [ "deer", "door", "cake", "card" ]

isUnique("dear") -> false
isUnique("cart") -> true
isUnique("cane") -> false
isUnique("make") -> true

 1 public class ValidWordAbbr {
 2     String[] dict;
 3     HashMap<String, Set<String>> afterAbbr;
 4
 5     public ValidWordAbbr(String[] dictionary) {
 6         this.dict = dictionary;
 7         this.afterAbbr = new HashMap<String, Set<String>>();
 8         for (String item : dictionary) {
 9             String str = abbr(item);
10             if (afterAbbr.containsKey(str)) {
11                 afterAbbr.get(str).add(item);
12             }
13             else {
14                 HashSet<String> set = new HashSet<String>();
15                 set.add(item);
16                 afterAbbr.put(str, set);
17             }
18         }
19     }
20
21     public boolean isUnique(String word) {
22         String str = abbr(word);
23         if (!afterAbbr.containsKey(str)) return true;
24         else if (afterAbbr.containsKey(str) && afterAbbr.get(str).contains(word) && afterAbbr.get(str).size()==1) return true;
25         return false;
26     }
27
28     public String abbr(String item) {
29         if (item == null) return null;
30         if (item.length() <= 2) return item;
31         StringBuffer res = new StringBuffer();
32         res.append(item.charAt(0));
33         res.append(item.length()-2);
34         res.append(item.charAt(item.length()-1));
35         return res.toString();
36     }
37 }
38
39
40 // Your ValidWordAbbr object will be instantiated and called as such:
41 // ValidWordAbbr vwa = new ValidWordAbbr(dictionary);
42 // vwa.isUnique("Word");
43 // vwa.isUnique("anotherWord");