1107 Social Clusters

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

人是并查集中的元素，合并依据为是否有相同爱好

该题需要反自然顺序输出合并完毕后每个小组的人数，可以利用桶排序先计算各小组人数，在为桶排序的索引排序

#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <vector>

using namespace std;

#define SUM 1001

struct Person {
    
    //不爱用vector数组
	vector<int> hobby;
};

int n, sum_hobby;
int f[SUM];//并查集数组
Person persons[SUM];

int query(int i) {
    
    //查询祖宗结点
	if (f[i] == i) {
    
    
		return f[i];
	} else {
    
    
		f[i] = query(f[i]);
		return f[i];
	}
}

void merge_hobby(int left, int right) {
    
    //合并两结点
	int t1 = query(left);
	int t2 = query(right);
	if (t1 != t2) {
    
    
		f[t2] = t1;
	}
}

int main() {
    
    
	cin >> n;
	for (int i = 1; i <= n; i++) {
    
    
		f[i] = i;
	}
	for (int i = 1; i <= n; i++) {
    
    
		int sum_h;
		cin >> sum_h;
		getchar();
		for (int j = 1; j <= sum_h; j++) {
    
    
			int temp;
			cin >> temp;
			persons[i].hobby.push_back(temp);
			for (int a = 1; a <= i; a++) {
    
    
				if (find(persons[a].hobby.begin(), persons[a].hobby.end(), temp)
					!= persons[a].hobby.end()) {
    
    //如果有相同的爱好，两点合并
					merge_hobby(a, i);
				}
			}
		}
	}
	int book[SUM] = {
    
     0 };
	for (int i = 1; i <= n; i++) {
    
    
		f[i] = query(f[i]);//有的点可能合并中路径压缩不彻底，有几个测试点检测该结果
		book[f[i]]++;//先记录各组的人数
		if (f[i] == i) {
    
    
			sum_hobby++;
		}
	}
	cout << sum_hobby << endl;
	sort(book, book + SUM, greater<int>{
    
    });//根据人数排序
	for (int i = 1; i <= sum_hobby; i++) {
    
    
		cout << book[i - 1];
		if (i != sum_hobby) {
    
    
			cout << " ";
		}
	}
	return 0;
}