P1790 小胡同学的连通图

 用并查集做

#include
#include
#include
#include
#include
using namespace std;
int par[105] = { 0 };
int rank0[105] = { 0 };
int root[105] = { 0 };

void init(int n) {
	for (int  i = 1; i <= n; i++)
	{
		par[i] = i;
		rank0[i] = 0;
	}
}

int find(int x) {
	if (par[x]==x)
	{
		return x;
	}
	else
	{
		return par[x] = find(par[x]);
	}

}

void unite(int x, int y) {
	x = find(x);
	y = find(y);

	if (x==y)
	{
		return;
	}

	if (rank0[x]> n >> m;

	init(n);

	int x, y;
	for (int i = 0; i < m; i++)
	{
		cin >> x >> y;
		unite(x, y);

	}

	for (int i = 1; i <= n; i++)
	{
			root[find(i)] = 1;
		
	}
	int num=0;
	for (int i = 1; i <=n; i++)
	{
		if (root[i]==1)
		{
			num++;
		}
	}

	num == 1 ? cout << "Yes" << endl : cout << "No" << endl;
    return 0;
}