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畅通工程

4 2
1 3
4 3
3 3
1 2
1 3
2 3
5 2
1 2
3 5
999 0
0

1
0
2
998

Hint
Hint
 
Huge input, scanf is recommended.

#include<cstdio>
int a[10000];
int find(int x)//查找x元所属的集合。
{
	int r = x;
	while (r != a[r])
		r = a[r];
	return r;
}
void unio(int x, int y)
{
	int fx, fy;
	fx = find(x);
	fy = find(y);
	if (a[fx] != fy)//如果不在一个集合那么将这两个集合合并。
		a[fx] = fy;//或者写为a[fy]=fx;
}

int main()
{
	int n, m,x,y;
	while (~scanf("%d", &n) && n)
	{
		int ans = -1;
		for (int i = 1; i <= n; i++)
			a[i] = i;
		scanf("%d", &m);
		while (m--)
		{
			scanf("%d%d", &x, &y);
			unio(x, y);
		}
		for (int i = 1; i <= n; i++)
		{
			if (a[i] == i)
				ans++;
		}
		printf("%d\n", ans);
	}
	return 0;
}

HDU 1232--并查集

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原文地址：http://blog.csdn.net/qq_24489717/article/details/45949929