PAT (Advanced Level) 1107 Social Clusters （30 分）

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

Code

#include <iostream>
#include <vector>
#include <algorithm>
#pragma warning(disable:4996)

using namespace std;

vector<int> father, isRoot;

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 fa = findFather(a);
	int fb = findFather(b);
	if (fa != fb)
		father[fa] = fb;
}

int main()
{
	int n;
	scanf("%d", &n);
	father.resize(n + 1);
	isRoot.resize(n + 1, 0);
	for (int i = 1; i < father.size(); i++)
		father[i] = i;
	vector<int> hobby(1001, 0);
	for (int i = 1; i <= n; i++)
	{
		int num;
		scanf("%d: ", &num);
		for (int j = 0; j < num; j++)
		{
			int h; scanf("%d", &h);
			if (hobby[h] == 0)
				hobby[h] = i;
			Union(i, findFather(hobby[h]));
		}
	}
	for (int i = 1; i <= n; i++)
		isRoot[findFather(i)]++;
	int cnt = 0;
	for (int i = 1; i <= n; i++)
		if (isRoot[i] > 0)
			cnt++;
	printf("%d\n", cnt);
	sort(isRoot.begin(), isRoot.end(), [](const int n1, const int n2)->bool {
		return n1 > n2;
	});
	for (int i = 0; i < cnt; i++)
		printf("%d%c", isRoot[i], (i == cnt - 1 ? '\n' : ' '));
	return 0;
}

思路：

膜柳神 https://blog.youkuaiyun.com/liuchuo/article/details/52191082