<poj-1611>The Suspects

忘是亡心i 2022-07-15 08:56 124阅读 0赞

The Suspects

<table> 
 <tbody> 
  <tr> 
   <td><strong>Time Limit:</strong>&nbsp;1000MS</td> 
   <td>&nbsp;</td> 
   <td><strong>Memory Limit:</strong>&nbsp;20000K</td> 
  </tr> 
  <tr> 
   <td><strong>Total Submissions:</strong>&nbsp;34781</td> 
   <td>&nbsp;</td> 
   <td><strong>Accepted:</strong>&nbsp;16883</td> 
  </tr> 
 </tbody> 
</table>

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

解题思路

明明说是简单并查集的使用，其实在做这个题的时候大致的思路还是对的，但是因为一点习惯上的问题

还有就是我的并查集是现学的，可能理解的不太好，一个小的细节让我调试的很久还是没看出来

#include<stdio.h>
    #include<string.h>
    
    int pre[30000];
    int ch[30000];
    
    int find(int x)
    {
        int r = x;//查找上一级
        while(r != pre[r])
        {
            r = pre[r];
        }
        int i = x, t;
        while(i != r)//压缩路径
        {
            t = pre[i];
            pre[i] = r;
            i = t;
        }
        return r;
    }
    
    void join(int x, int y)//合并
    {
        x = find(x);
        y = find(y);
        if(x != y)
        {
            pre[y] = x;
        }
    }
    
    int main()
    {
        int n, m;
        int t;
        while(scanf("%d %d",&n, &m)!=EOF)
        {
            memset(pre, 30001, sizeof(pre));
            int count = 0;
            if(n == 0&&m == 0) break;
            for(int i = 0; i <= n-1; i++)
            {
                pre[i] = i;
            }
            for(int i = 1; i <= m; i++)
            {
                scanf("%d",&t);
                for(int j = 0; j <= t-1; j++)
                {
                    scanf("%d",&ch[j]);
                }
                for(int j = 0; j < t-1; j++)
                {
                    join(ch[j], ch[j+1]);
                }
            }
            for(int i = 0; i <= n-1; i++)
            {
                if(find(i) == find(0))
                    count++;
            }
            printf("%d\n",count);
        }
        return 0;
    }