POJ--1611 -- The Suspects [并查集]

The Suspects

Time Limit: 1000MS
Memory Limit: 20000KTotal Submissions: 18829
Accepted: 9113

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

Code:

数组下标代表学生,存放元素代表group号,

每输入一个元素都把和0相关的都更新(他们的group号一定是一样的),虽然这样每次都得扫描一遍,但是这种方法还是可行的~

,最后数和0相等有多少就阔以啦~

#include"stdio.h"#include"iostream"#include"string.h"using namespace std;int main(){int st[30005];int stu,group,i,j,k,c,temp,sum,n;while(scanf("%d%d",&stu,&group),stu||group)//0行0列不存放学生 {sum=0;memset(st,0,sizeof(st)); st[0] = -1;for(i=1;i<=group;i++){scanf("%d",&n);//一组人数 for(j=1;j<=n;j++){scanf("%d",&temp);//学生号if(st[temp]){c = st[temp];for(k=0;k<30005;k++)if(st[k] == c) st[k] = i;}else st[temp] = i;}}for(i=0;i<30005;i++){if(st[i]==st[0]) sum++;}printf("%d\n",sum);//printf("----\n");}return 0;}