1107 Social Clusters (30)（30 分）

When register on a social network, you are always asked to specify your hobbies in order to find some potential friends with the same hobbies. A "social cluster" is a set of people who have some of their hobbies in common. You are supposed to find all the clusters.

Input Specification:

Each input file contains one test case. For each test case, the first line contains a positive integer N (<=1000), the total number of people in a social network. Hence the people are numbered from 1 to N. Then N lines follow, each gives the hobby list of a person in the format:

K~i~: h~i~[1] h~i~[2] ... h~i~[K~i~]

where K~i~ (>0) is the number of hobbies, and h~i~[j] is the index of the j-th hobby, which is an integer in [1, 1000].

Output Specification:

For each case, print in one line the total number of clusters in the network. Then in the second line, print the numbers of people in the clusters in non-increasing order. The numbers must be separated by exactly one space, and there must be no extra space at the end of the line.

Sample Input:

8
3: 2 7 10
1: 4
2: 5 3
1: 4
1: 3
1: 4
4: 6 8 1 5
1: 4

Sample Output:

3
4 3 1
题意很明显，求有某些相同爱好的人的集合的人数。
并查集，凡是有相同的爱好的人都归到一个集合里，最后查一下每一个集合里的人数，存下来，降序排序输出。
代码：

#include <stdio.h>
#include <stdlib.h>
int n,m,d,c,f[1001],mp[1001][1001],num[1001],ans[1001];
void init() {
    for(int i = 1;i <= n;i ++) {
        f[i] = i;
    }
}
int getf(int x) {
    if(x != f[x])f[x] = getf(f[x]);
    return f[x];
}
void mer_(int x,int y) {
    int xx = getf(x),yy = getf(y);
    f[xx] = yy;
}
int cmp(const void *a,const void *b) {
    return *(int *)b - *(int *)a;
}
int main() {
    scanf("%d",&n);
    init();
    for(int i = 1;i <= n;i ++) {
        scanf("%d:",&m);
        for(int j = 1;j <= m;j ++) {
            scanf("%d",&d);
            mp[i][d] = 1;
            for(int k = 1;k < i;k ++) {
                if(mp[k][d])mer_(k,i);
            }
        }
    }
    for(int i = 1;i <= n;i ++) {
        int e = getf(i);
        num[e] ++;
    }
    for(int i = 1;i <= n;i ++) {
        if(num[i])ans[c ++] = num[i];
    }
    qsort(ans,c,sizeof(int),cmp);
    printf("%d\n",c);
    for(int i = 0;i < c;i ++) {
        if(i)putchar(' ');
        printf("%d",ans[i]);
    }
}