poj 1611 The Suspects(简单并查集)

The Suspects

Time Limit: 1000MS		Memory Limit: 20000K
Total Submissions: 28195		Accepted: 13741

Description

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：在一个学校，有n个学生（编号为0~n-1）和m个社团，其中0号学生是有可能感染非典的，只要和有可能感染非典的人在一个社团，那么这个人就有可能会被感染并且要被隔离，问被隔离的总人数。
　　　　首先输入n和m，然后是m行，每行的开始是一个k，表示社团有k个人。

#include <iostream>
#include <stdio.h>
using namespace std;
#define MAX 30005
int father[MAX],num[MAX];
void make_set(int n)
{
    for(int i=0;i<n;i++)
    {
        father[i]=i;
        num[i]=1;
    }
}
int find(int x)
{
    return father[x]==x?x:father[x]=find(father[x]);
}
void Union(int u,int v)
{
    int x,y;
    x=find(u);
    y=find(v);
    if(x!=y)
    {
        num[y]+=num[x];
        father[x]=y;
    }
}
int main()
{
    int n,m,k,u,v;
    while(~scanf("%d%d",&n,&m),n||m)
    {
        make_set(n);
        while(m--)
        {
            scanf("%d%d",&k,&u);
            for(int i=1;i<k;i++)
            {
                scanf("%d",&v);
                Union(u,v);
            }
        }
        printf("%d
",num[find(0)]);
    }
    return 0;
}