[并查集]LA 3644 X-Plosives

 

#include <cstdio>

#include <cstring>



const int INF=0x3f3f3f3f;

const int MAXN=1e5+10;



int parent[MAXN];

int findset(int a){

	return parent[a]!=a ? parent[a] = find(parent[a]) :a ;

}

int main()

{

	int a,b,ans=0,x,y;

	while(scanf("%d",&a)==1 ){

		for(int i=0;i<MAXN;++i)parent[i]=i;

		ans=0;

		while(a!=-1){

			scanf("%d",&b);

			x=findset(a);y=findset(b);

			if(x==y)ans++;

			else parent[y]=x;

			scanf("%d",&a);

		}

		printf("%d\n", ans);

	}	

	return 0;

}