UVa 1160 X-Plosives (并查集)

/*0.015s*/

#include <cstdio>
#include<cstring>
const int mx = 100005;

int fa[mx], rk[mx];

int find(int x) {return ~fa[x] ? fa[x] = find(fa[x]) : x;}

///其实不用启发式合并也行，毕竟数据量超小
void merge(int x, int y)
{
	if (rk[x] < rk[y]) fa[x] = y;
	else
	{
		fa[y] = x;
		if (rk[x] == rk[y]) ++rk[x];
	}
}

int main()
{
	int x, y;
	while (~scanf("%d", &x))
	{
		memset(fa, -1, sizeof(fa));
		memset(rk, 0, sizeof(rk));
		int refusals = 0;
		while (x != -1)
		{
			scanf("%d", &y);
			x = find(x), y = find(y);
			if (x == y) ++refusals; /// 如果x和y在同一个集合，则拒绝
			else merge(x, y); /// 否则合并
			scanf("%d", &x);
		}
		printf("%d\n", refusals);
	}
	return 0;
}