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 42 1 25 10 13 11 12 142 0 12 99 2200 21 55 1 2 3 4 51 00 0

Sample Output

411

   题意：有N个学生，编号为0-n-1;这些学生加入了不同的组织，和嫌疑人在一个组织的也会被认为成嫌疑人，题中将0号学生定义为嫌疑人，所以就是要找和0号同学在一个组织的有多少人。

思路：并查集的模板题，没什么思路。。。。

下面附上代码：

#include<cstdio>#define max 31000int a[max]; int pre[max];int find(int x){int r=x;while(r!=pre[r]) r=pre[r];int i=x,j;while(pre[i]!=r){j=pre[i];pre[i]=r;i=j;}return r;}//寻找根接点 void AA(int n){int i;for(i=0;i<n;i++) pre[i]=i;}void HB(int x,int y){int fx=find(x),fy=find(y);if(fx!=fy) pre[fy]=fx;//合并 }int main(){int n,m,k;while(scanf("%d %d",&n,&m)!=EOF&&(m+n)){AA(n);for(int i=0;i<m;i++){scanf("%d",&k);for(int j=0;j<k;j++){scanf("%d",&a[j]);if(j>0) HB(a[j],a[j-1]);}}int sum=1;for(int i=1;i<n;i++){if(find(i)==find(0)) sum++;}printf("%d\n",sum);}}