1107 Social Clusters (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

#include<iostream>
#include<cstring>
#include<algorithm>
#include<vector>

using namespace std;

const int N=1010;

int n;
vector<int> hobby[N];  //每个爱好有哪些人
int p[N];
int cnt[N];   //统计每个社群多少人

int find(int x)
{
    if(p[x]!=x) p[x]=find(p[x]);
    return p[x];
}

int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        int cnt;
        scanf("%d:",&cnt);
        while(cnt--)
        {
            int h;
            cin>>h;
            hobby[h].push_back(i);
        }
    }

    for(int i=1;i<=n;i++) p[i]=i;

    for(int i=1;i<=1000;i++)
        for(int j=1;j<hobby[i].size();j++)
        {
            int a=hobby[i][0],b=hobby[i][j];
            p[find(a)]=find(b);
        }

    for(int i=1;i<=n;i++) cnt[find(i)]++;

    sort(cnt,cnt+n+1,greater<int>());  //第一个不用，多加一个1

    int k=0;
    while(cnt[k]) k++;

    cout<<k<<endl;
    cout<<cnt[0];
    for(int i=1;i<k;i++) cout<<' '<<cnt[i];
    cout<<endl;

    return 0; 
}