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

 package fbOnsite;
 import java.util.*;
 class UnionFind{
     int[] ids;
     int count;
     public UnionFind(int num) {
         ids = new int[num];
         Arrays.fill(ids, -1);
         count = 0;
     }

     public int find(int id) {
         while (id != ids[id]) id = ids[id];
         return id;
     }

     public void union(int n1, int n2) {
         int root1 = find(n1);
         int root2 = find(n2);
         ids[root2] = root1;
     }

     public boolean isConnected(int n1, int n2) {
         return find(n1) == find(n2);
     }
 }

 public class EmailUser {
     public int commonUser(HashMap<Integer, List<Character>> map) {
         int size = map.size();
         UnionFind uf = new UnionFind(10);
         HashMap<Character, Integer> emailToUser = new HashMap<Character, Integer>();
         for (int user : map.keySet()) {
             uf.ids[user] = user;
             uf.count++;
             List<Character> emailList = map.get(user);
             for (Character eachEmail : emailList) {
                 if (!emailToUser.containsKey(eachEmail)) {
                     emailToUser.put(eachEmail, user);
                 }
                 else {
                     int oriUser = emailToUser.get(eachEmail);
                     if (!uf.isConnected(user, oriUser)) {
                         uf.union(oriUser, user);
                         uf.count--;
                     }
                 }
             }
         }
         for (int elem : uf.ids)
             System.out.print(elem);
         return uf.count;
     }

     /**
      * @param args
      */
     public static void main(String[] args) {
         // TODO Auto-generated method stub
         EmailUser sol = new EmailUser();
         HashMap<Integer, List<Character>> map = new HashMap<Integer, List<Character>>();
         map.put(0, new ArrayList<Character>());
         map.put(1, new ArrayList<Character>());
         map.put(2, new ArrayList<Character>());
         map.put(3, new ArrayList<Character>());
         map.put(4, new ArrayList<Character>());
         map.put(5, new ArrayList<Character>());
         map.put(6, new ArrayList<Character>());
         map.get(0).add('x');
         map.get(0).add('y');
         map.get(0).add('z');
         map.get(1).add('x');
         map.get(2).add('a');
         map.get(2).add('b');
         map.get(3).add('y');
         map.get(3).add('z');
         map.get(4).add('b');
         map.get(5).add('m');
         map.get(6).add('t');
         map.get(6).add('b');
         int res = sol.commonUser(map);
         System.out.println(res);
     }

 }