FB面經Prepare: Email User

有一些帳號，帳號裏面有一個或多個email， 若是兩個帳號有共同的email，則認爲這兩個帳號是同一我的，找出哪些帳號是同一我的
輸入是這樣的:數字是用戶，字母是郵箱，有不少人有多個郵箱，找出相同的用戶
  1- {x,y,z}
  2-{x} 
  3-{a,b}
  4-{y, z}
  5-{b}
  6-{m}
  7-{t,b}

帳號之間若是有公共email就連邊，我以爲要用hashMap, 存（email, user） pair

若是當前user的某個email在hashMap裏出現過，當時是user1, 就看user和user1是否connected，否的話就要union,根據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<Integer, List<Character>> map) {
30         int size = map.size();
31         UnionFind uf = new UnionFind(10);
32         HashMap<Character, Integer> emailToUser = new HashMap<Character, Integer>();
33         for (int user : map.keySet()) {
34             uf.ids[user] = user;
35             uf.count++;
36             List<Character> 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<Integer, List<Character>> map = new HashMap<Integer, List<Character>>();
62         map.put(0, new ArrayList<Character>());
63         map.put(1, new ArrayList<Character>());
64         map.put(2, new ArrayList<Character>());
65         map.put(3, new ArrayList<Character>());
66         map.put(4, new ArrayList<Character>());
67         map.put(5, new ArrayList<Character>());
68         map.put(6, new ArrayList<Character>());
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 }