PAT 1107 Social Clusters （30 分）

解析

#include
#include
#include
using namespace std;
const int maxn = 1010;
int hobby[maxn]{0};
bool isroot[maxn]{ false };
int findFather(int x) {
	if (x == hobby[x])    //father
		return x;
	else
		return hobby[x] = findFather(hobby[x]);
}
void Union(int a, int b) {
	int fa = findFather(a);
	int fb = findFather(b);
	if (fa != fb) 
		hobby[fa] = fb; //let fa`s father is fb
}
int main()
{
	for (int i = 0; i < maxn; i++) 
		hobby[i] = i;   //set i`s father is itself
	int N;
	scanf("%d", &N);
	vector<int> people(N+1);
	for (int i = 0; i < N; i++) {
		int K;
		scanf("%d:", &K);
		vector<int> clust(K);
		for (int j = 0; j < K; j++) {
			scanf("%d", &clust[j]);
		}
		people[i + 1] = clust[0];
		if (K >= 1) {
			for (int j = 1; j < K; j++)
				Union(clust[j], clust[j - 1]);
		}
	}
	for (int i = 0; i < N; i++) {
		people[i + 1] = findFather(people[i + 1]);
		isroot[people[i + 1]] = true;
	}
	vector<int> Cluster;
	for (int i = 0; i < maxn; i++) {
		if (isroot[i] == true)
			Cluster.push_back(count(people.cbegin(), people.cend(), i));
	}
	sort(Cluster.begin(), Cluster.end());
	printf("%d\n", Cluster.size());
	for (auto it = Cluster.crbegin(); it != Cluster.crend(); it++)
		printf("%d%c", *it,it+1==Cluster.crend()?'\n':' ');
}