HDU 1232 (Smooth Traffic Project)

Use disjoint-set , apply the basic template.

#include <iostream>
using namespace std;
const int MAXN = 1005;

int father[MAXN]; //父结点

//初始化并查集
void makeSet(int n)
{
	for (int i = 1; i <= n; i++)
		father[i] = i;
}

//查找x所在集合的代表元素（所在树的根结点）
int find(int x)
{
	if (x != father[x])
		father[x] = find(father[x]);
	return father[x];
}

//合并x所在集合和y所在集合
void unionSet(int x, int y)
{
	int fx = find(x);
	int fy = find(y);
	if (fx != fy)
		father[fx] = fy;
}

int main()
{
	int N, M;
	while (cin >> N)
	{
		if (N == 0)
			break;
		cin >> M;

		makeSet(N);

		int A, B;
		for (int i = 0; i < M; i++)
		{
			cin >> A >> B;
			unionSet(A, B);
		}

		int road = 0; //修路数量
		for (int i = 1; i <= N; i++)
		{
			if (i == father[i])
				++road;
		}
		cout << --road << endl;
	}
	return 0;
}

Keep up.