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
1 package fb;
2
3 import java.util.*;
4
5 public class ReferFriends {
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 }
44
45 public List<String> getFriends(String name) {
46 HashMap<String, List<String>> map = new HashMap<String, List<String>>();
47 map.put("Lily", new ArrayList<String>());
48 map.put("Lucy", new ArrayList<String>());
49 map.put("Hanmeimei", new ArrayList<String>());
50 map.put("Jim", new ArrayList<String>());
51 map.put("Lilei", new ArrayList<String>());
52 map.put("Poly", new ArrayList<String>());
53 map.get("Lily").add("Lilei");
54 map.get("Lily").add("Poly");
55 map.get("Lily").add("Hanmeimei");
56 map.get("Lily").add("Jim");
57 map.get("Lucy").add("Lilei");
58 map.get("Lucy").add("Poly");
59 map.get("Lucy").add("Hanmeimei");
60 map.get("Lucy").add("Lily");
61 map.get("Lilei").add("Jim");
62 map.get("Lilei").add("Lucy");
63 map.get("Lilei").add("UncleWang");
64 map.get("Lilei").add("Hanmeimei");
65 map.get("Lilei").add("Lily");
66 map.get("Jim").add("Lily");
67 map.get("Jim").add("Lucy");
68 map.get("Jim").add("Lilei");
69 map.get("Poly").add("Jim");
70 map.get("Poly").add("Lilei");
71 return map.get(name);
72 }
73
74 /**
75 * @param args
76 */
77 public static void main(String[] args) {
78 // TODO Auto-generated method stub
79 ReferFriends sol = new ReferFriends();
80 //List<String> res = sol.recommendation("Poly");
81 List<String> res = sol.recommendation("Jim");
82 for (String each : res) {
83 System.out.println(each);
84 }
85 }
86
87 }
