FB面经Prepare: Email User

有一些账号，账号里面有一个或多个email， 如果两个账号有共同的email，则认为这两个账号是同一个人，找出哪些账号是同一个人
输入是这样的:数字是用户，字母是邮箱，有很多人有多个邮箱，找出相同的用户
  1- {x,y,z}
  2-{x} 
  3-{a,b}
  4-{y, z}
  5-{b}
  6-{m}
  7-{t,b}

账号之间如果有公共email就连边，我觉得要用hashMap, 存（email, user） pair

如果当前user的某个email在hashMap里出现过，当时是user1, 就看user和user1是否connected，否的话就要union,根据Union Find

Union Find Based on Quick Union

 1 package fbOnsite;
 2 import java.util.*;
 3 class UnionFind{
 4     int[] ids;
 5     int count;
 6     public UnionFind(int num) {
 7         ids = new int[num];
 8         Arrays.fill(ids, -1);
 9         count = 0;
10     }
11     
12     public int find(int id) {
13         while (id != ids[id]) id = ids[id];
14         return id;
15     }
16     
17     public void union(int n1, int n2) {
18         int root1 = find(n1);
19         int root2 = find(n2);
20         ids[root2] = root1;
21     }
22     
23     public boolean isConnected(int n1, int n2) {
24         return find(n1) == find(n2);
25     }
26 }
27 
28 public class EmailUser {
29     public int commonUser(HashMap> map) {
30         int size = map.size();
31         UnionFind uf = new UnionFind(10);
32         HashMap emailToUser = new HashMap();
33         for (int user : map.keySet()) {
34             uf.ids[user] = user;
35             uf.count++;
36             List emailList = map.get(user);
37             for (Character eachEmail : emailList) {
38                 if (!emailToUser.containsKey(eachEmail)) {
39                     emailToUser.put(eachEmail, user);
40                 }
41                 else {
42                     int oriUser = emailToUser.get(eachEmail);
43                     if (!uf.isConnected(user, oriUser)) {
44                         uf.union(oriUser, user);
45                         uf.count--;
46                     }
47                 }
48             }
49         }
50         for (int elem : uf.ids)
51             System.out.print(elem);
52         return uf.count;
53     }
54 
55     /**
56      * @param args
57      */
58     public static void main(String[] args) {
59         // TODO Auto-generated method stub
60         EmailUser sol = new EmailUser();
61         HashMap> map = new HashMap>();
62         map.put(0, new ArrayList());
63         map.put(1, new ArrayList());
64         map.put(2, new ArrayList());
65         map.put(3, new ArrayList());
66         map.put(4, new ArrayList());
67         map.put(5, new ArrayList());
68         map.put(6, new ArrayList());
69         map.get(0).add('x');
70         map.get(0).add('y');
71         map.get(0).add('z');
72         map.get(1).add('x');
73         map.get(2).add('a');
74         map.get(2).add('b');
75         map.get(3).add('y');
76         map.get(3).add('z');
77         map.get(4).add('b');
78         map.get(5).add('m');
79         map.get(6).add('t');
80         map.get(6).add('b');
81         int res = sol.commonUser(map);
82         System.out.println(res);
83     }
84 
85 }