POJ 1611 The Suspects

点击打开链接

The Suspects

Time Limit: 1000MS Memory Limit: 20000KTotal Submissions: 17392 Accepted: 8387

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

Sample Output

411

Source

Asia Kaohsiung 2003

题意：SARS病毒传播非常厉害，将得了病毒的学生定义为嫌疑人，学校为了防止更多的人的这种病毒，就将他们进行隔离。现在有m个学习小组，每个学习小组有k个人，而且一个人可以参加多个学习小组，如果学习小组有一个嫌疑人，则定义这个小组的所有人都为嫌疑人，现定义0号学生为嫌疑人，让你求嫌疑人最多是多少。

思路：将每个小组当做一个集合，并且记录每个集合最大的个数，组后找出0所在的集合的最多的个数即为所求。

#include<stdio.h>int pre[30007],num[30007];void init(){    int i;    for(i=0;i<30007;i++)    {        pre[i]=i;//记录父节点        num[i]=1;//记录个数    }}int find(int x){    while(x!=pre[x])    x=pre[x];    return x;}void uion(int x,int y){    if(x==y)return;    if(num[x]>num[y])    {        pre[y]=x;        num[x]+=num[y];    }    else    {        pre[x]=y;        num[y]+=num[x];    }}int main(){    int n,m,i,j,a,b,x,y;    while(scanf("%d%d",&n,&m),n|m)    {        init();        for(j=0;j<m;j++)        {            int k;            scanf("%d",&k);            scanf("%d",&a);            for(i=1;i<k;i++)            {                scanf("%d",&b);                x=find(a);                y=find(b);                uion(x,y);//合并集合            }        }        printf("%d\n",num[find(0)]);    }    return 0;}