Friends Recommendation - FB Prepare

http://www.cnblogs.com/EdwardLiu/p/6399921.html

有个getFriend() API, 让你推荐你的朋友的朋友做你的朋友，当然这个新朋友不能是你原来的老朋友

 6     public List<String> recommendation(String name) {
 7         List<String> res = new ArrayList<String>();
 8         if (name==null || name.length()==0) return res;
 9         
10         List<String> friends = getFriends(name);
11         HashSet<String> set = new HashSet<String>();
12         for (String friend : friends) {
13             set.add(friend);
14         }
15         
16         HashMap<String, Integer> map = new HashMap<String, Integer>();
17         ArrayList<String>[] list = new ArrayList[friends.size()+1];
18         
19         for (String friend : friends) {
20             List<String> ffriends = getFriends(friend);
21             for (String each : ffriends) {
22                 if (!set.contains(each) && !each.equals(name)) {
23                     //map.put(each, map.getOrDefault(each, 0) + 1);
24                     if (map.containsKey(each))
25                         map.put(each, map.get(each)+1);
26                     else map.put(each, 1);
27                 } 
28             }
29         }
30         
31         for (String each : map.keySet()) {
32             int count = map.get(each);
33             if (list[count] == null) list[count] = new ArrayList<String>();
34             list[count].add(each);
35         }
36         
37         for (int k=list.length-1; k>=0; k--) {
38             if (list[k] != null) 
39                 res.addAll(list[k]);
40         }
41         return res;
42         
43     }