1107. Social Clusters (30)

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.

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

3
4 3 1

#include <bits/stdc++.h>
#include<vector>
#define ms(x,y) memset(x,y,sizeof(x))
const int M=1e5+10;
using namespace std;
int i,j,k,n,m;
int pre[M];
int father[M];

int findf(int x)
{
    int z=x;
    while(z!=pre[z])
        z=pre[z];
    while(pre[x]!=z){
        int k=pre[x];
        pre[x]=z;
        x=k;
    }
    return z;
}

void Union(int a,int b)
{
    int aa=findf(a);
    int bb=findf(b);
    if(aa!=bb){
        pre[aa]=bb;
    }
}

int main()
{
    int course[1001];
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        pre[i]=i;
    for(int i=1;i<=n;i++){
        int k;
        scanf("%d:",&k);
        for(int j=0;j<k;j++){
            int t;scanf("%d",&t);
            if(course[t]==0)course[t]=i;
            Union(i,course[t]);
        }
    }
    int ans=0,cnt[M];
    memset(cnt,0,sizeof(cnt));
    for(int i=1;i<=n;i++)cnt[findf(i)]++;
    for(int i=1;i<=n;i++){
        if(cnt[i]!=0)ans++;
    }
    printf("%d\n",ans);
    sort(cnt+1,cnt+n+1);
    for(int i=n;i>n-ans;i--){
        if(i<n)printf(" %d",cnt[i]);
        else printf("%d",cnt[i]);
    }
    return 0;
}