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);
    }

}