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.

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<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 1010;
int course[maxn] = {0};
int father[maxn];
int isRoot[maxn] = {0};

int findFather(int x){
    int a = x;
    while(x != father[x]){
        x = father[x];
    }
    while(a != father[a]){
        int z = a;
        a = father[a];
        father[z] = x;
    }
    return x;
}


void Union(int a,int b){
    int faA = findFather(a);
    int faB = findFather(b);
    if(faA != faB) father[faA] = faB;
       
}

void init(int n){
    for(int i = 1; i <= n; i++){
        father[i] = i;
    }
    
}

bool cmp(int a,int b){
    return a > b;
}

int main(){
    
    int n,k,h;
    scanf("%d",&n);
    init(n);
    for(int i = 1; i <= n; i++){
        scanf("%d:",&k);
        for(int j = 0; j < k; j++){
            scanf("%d",&h);
            if(course[h] == 0){
                course[h] = i;
            }
            Union(i,findFather(course[h]));   //将course[h] == i号人归类 
        }
    }
    for(int i = 1; i <= n; i++){
        isRoot[findFather(i)]++;  //i的根节点的个数为社交圈的个数 
    }
    int ans = 0;
    for(int i = 1; i <= n; i++){
        if(isRoot[i] != 0) ans++;
    }
    printf("%d\n",ans);
    sort(isRoot+1,isRoot+n+1,cmp);
    for(int i = 1; i <= ans; i++){
        printf("%d",isRoot[i]);
        if(i < ans)printf(" ");
    }
    return 0;
}