题目地址

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 <vector>
#include<algorithm>
#include <cmath>
#include<map>
#include<cstring>
#include<queue>
#include<string>            //同一属性元素的集合，祖先是第一个有这属性的人；
#include<set>
#include<stack>
using namespace std;
typedef long long ll;
const int maxn=1010,inf=100000000;
int n,k,book[maxn]={0},fa[maxn];
int find(int x){
    int a=x;
    while(x!=fa[x]) x=fa[x];
    while(a!=fa[a]){
        int t=a;
        a=fa[a];
        fa[t]=x;
    }
    return x;               //忘了一次有一次有一次；
}
void union_it(int a,int b){
    int fx=find(a),fy=find(b);
    if(fx!=fy) fa[fx]=fy;
}
bool cmp(int a,int b){
    return a>b;
}
int main(){
    cin>>n;int act;
    for(int i=1;i<=n;i++) fa[i]=i;
    for(int i=1;i<=n;i++){
        scanf("%d:",&k);
        for(int j=0;j<k;j++){
            cin>>act;
            if(!book[act]) book[act]=i;         //book活动的祖先是人，father人的祖先是人；
            union_it(i,book[act]);          //每输入一个互动，这个人就并入该活动祖先；并查集每个集是元素；是将众多有相同点的元素并起来；
        }
    }
    int exsit[maxn]={0};
    for(int i=1;i<=n;i++){
         exsit[find(i)]++;
    }
    sort(exsit+1,exsit+1+n,cmp);int cnt=0;              //全文别搞混1到n还是0到n；
    for(int i=1;i<=n;i++) if(exsit[i]) cnt++;
    cout<<cnt<<endl;
    sort(exsit+1,exsit+1+n,cmp);
    for(int i=1;i<=cnt;i++){
        if(i!=1) cout<<" ";
        cout<<exsit[i];
    }
}