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【北大夏令營筆記-並查集】poj1611-The Suspects
The SuspectsTime Limit: 1000MS Memory Limit: 20000K
Total Submissions: 21517 Accepted: 10422
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
Source
Asia Kaohsiung 2003
//題意，有一些學生，加入了一些社團，包括0。一旦0患病，和他有關的人（同一團體）都是嫌疑對象。
問有多少嫌疑對象
//思路：並查集，將所有與0有關的人都放在同一集合，並把與0有關的人所在的社團的所有人數統計
AC代碼：
#include<stdio.h>
#define MAX 30000
int parent[MAX+10];
int total[MAX+10];
//total[Get_Root(a)]是a所在社團的人數
int Get_Root(int x)
{
//獲取a的根，並把a父節點改為根
if(parent[x]!=x)
parent[x]=Get_Root(parent[x]);
return parent[x];
}
void Merge(int x,int y)
{
x=Get_Root(x);
y=Get_Root(y);
if(x==y)
return;
parent[y]=x;
total[x]+=total[y];
}
int main()
{
int i,j,n,m,k,x,y;
while(scanf("%d %d",&n,&m)!=EOF)
{
if(n==0&&m==0)
break;
for(i=0;i<n;i++)
{
parent[i]=i;
total[i]=1;
}
for(i=0;i<m;i++)
{
scanf("%d",&x);
scanf("%d",&k);
x--;
while(x--)
{
scanf("%d",&y);
Merge(k,y);
}
}
printf("%d\n",total[Get_Root(0)]);
}
return 0;
}
最後更新：2017-04-03 05:39:19