*HDU3172 并查集

Posted 2020-08-17 LuZhiyuan

Virtual Friends

Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 8165    Accepted Submission(s): 2345

Problem Description

These days, you can do all sorts of things online. For example, you can use various websites to make virtual friends. For some people, growing their social network (their friends, their friends‘ friends, their friends‘ friends‘ friends, and so on), has become an addictive hobby. Just as some people collect stamps, other people collect virtual friends.

Your task is to observe the interactions on such a website and keep track of the size of each person‘s network.

Assume that every friendship is mutual. If Fred is Barney‘s friend, then Barney is also Fred‘s friend.

 

 

Input

Input file contains multiple test cases.
The first line of each case indicates the number of test friendship nest.
each friendship nest begins with a line containing an integer F, the number of friendships formed in this frindship nest, which is no more than 100 000. Each of the following F lines contains the names of two people who have just become friends, separated by a space. A name is a string of 1 to 20 letters (uppercase or lowercase).

 

 

Output

Whenever a friendship is formed, print a line containing one integer, the number of people in the social network of the two people who have just become friends.

 

 

Sample Input

1

3

Fred Barney

Barney Betty

Betty Wilma

 

 

Sample Output

2

3

4

 

 

Source

University of Waterloo Local Contest 2008.09

 

题意：

朋友的朋友是朋友，每输入一对朋友后问一共有几对朋友。

代码：

 1 //用map把字符串转化为数字。初始化时初始2*n个会超时。
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<map>
 6 using namespace std;
 7 int t,n;
 8 int num[100005],fat[100005];
 9 map<string,int>m;
10 int find(int x)
11 {
12     int rt=x;
13     while(fat[rt]!=rt)
14     {
15         rt=fat[rt];
16     }
17     int i=x,j;
18     while(i!=rt)
19     {
20         j=fat[i];
21         fat[i]=rt;
22         i=j;
23     }
24     return rt;
25 }
26 void connect(int x,int y)
27 {
28     int xx=find(x),yy=find(y);
29     if(xx!=yy)
30     {
31         fat[xx]=yy;
32         num[yy]+=num[xx];
33         printf("%d\n",num[yy]);
34     }
35     else printf("%d\n",num[yy]);
36 }
37 int main()
38 {
39     char ch1[25],ch2[25];
40     while(scanf("%d",&t)!=EOF)
41     {
42         while(t--)
43         {
44             scanf("%d%d",&n);
45             for(int i=0;i<=100000;i++)   //开大了会超时
46             {
47                 fat[i]=i;
48                 num[i]=1;
49             }
50             m.clear();
51             int cnt=1;
52             for(int i=1;i<=n;i++)
53             {
54                 scanf("%s%s",ch1,ch2);
55                 if(!m[ch1]) m[ch1]=cnt++;
56                 if(!m[ch2]) m[ch2]=cnt++;
57                 connect(m[ch1],m[ch2]);
58             }
59         }
60     }
61     return 0;
62 }