1.26寒假集训（并查集三连←.←）-2

愉（智）快（熄）的并查集练习↓

A - The Suspects

 

Severe acute respiratory syndrome (SARS), an atypical pneumonia of unknown aetiology, was recognized as a global threat in mid-March 2003. To minimize transmission to others, the best strategy is to separate the suspects from others. 
In the Not-Spreading-Your-Sickness University (NSYSU), there are many student groups. Students in the same group intercommunicate with each other frequently, and a student may join several groups. To prevent the possible transmissions of SARS, the NSYSU collects the member lists of all student groups, and makes the following rule in their standard operation procedure (SOP). 
Once a member in a group is a suspect, all members in the group are suspects. 
However, they find that it is not easy to identify all the suspects when a student is recognized as a suspect. Your job is to write a program which finds all the suspects.

Input

The input file contains several cases. Each test case begins with two integers n and m in a line, where n is the number of students, and m is the number of groups. You may assume that 0 < n <= 30000 and 0 <= m <= 500. Every student is numbered by a unique integer between 0 and n−1, and initially student 0 is recognized as a suspect in all the cases. This line is followed by m member lists of the groups, one line per group. Each line begins with an integer k by itself representing the number of members in the group. Following the number of members, there are k integers representing the students in this group. All the integers in a line are separated by at least one space. 
A case with n = 0 and m = 0 indicates the end of the input, and need not be processed.

Output

For each case, output the number of suspects in one line.

Sample Input

100 4
2 1 2
5 10 13 11 12 14
2 0 1
2 99 2
200 2
1 5
5 1 2 3 4 5
1 0
0 0

Sample Output

4
1
1

题意是：给出多组测试数据，n个学生，m组关系，0号同学是每组的传染源，若是一个集合中有人得病，该集合内其他人都一起狗带。输出每组测试数据有几个人挂掉。题源：https://vjudge.net/contest/209382#problem/A

#include<cstdio>
#include<cmath>
#include<algorithm>
#include<string>
#include<iostream>
using namespace std;

int fa[33333];

int findfa(int x)//找爸爸
{
	int a=x;
	while(x!=fa[x])
	{
		x=fa[x];
	}
	while(a!=fa[a])
	{
		int z=a;
		a=fa[a];
		fa[z]=x;
	}
	return x;
}

void uni(int a,int b)//合并小朋友
{
	int faa=findfa(a);
	int fab=findfa(b);
	if(faa!=fab)
	{
		fa[faa]=fab;
	}
}

int n,m,k,temp1,temp2;

int main()
{
	while(scanf("%d%d",&n,&m),n||m)
	{
		for(int i=0;i<n;i++)//初始化，自己是自己爸爸
			fa[i]=i;
		for(int i=0;i<m;i++)
		{
			cin>>k>>temp1;
			for(int j=1;j<k;j++)//把一组关系的小朋友合并成一个爸爸
			{
				cin>>temp2;
				uni(temp1,temp2);
			}
		}
		int t=findfa(0),count=1;
		for(int i=1;i<n;i++)
		{
			if(findfa(i)==t)
				count++;
		}
		printf("%d\n",count);
	}
	return 0;
}