hdu 3047 Zjnu Stadium (带权并查集)

# include <stdio.h>
# include <algorithm>
using namespace std;
int father[50010];
int dis[50010];
int fa,fb;
int find(int x)
{
	if(x!=father[x])
	{
		int p=father[x];
		father[x]=find(father[x]);
		dis[x]+=dis[p];
	}
	return father[x];
}
void Union(int x,int y,int l)
{
	father[fb]=fa;
	dis[fb]=dis[x]-dis[y]+l;//子结点到根结点距离
}
int main()
{
	int n,m,i,cot,a,b,k;
	while(~scanf("%d%d",&n,&m))
	{
		for(i=0;i<=n;i++)
			father[i]=i;
		memset(dis,0,sizeof(dis));
		cot=0;
		for(i=0;i<m;i++)
		{
			scanf("%d%d%d",&a,&b,&k);
			fa=find(a);
			fb=find(b);
			if(fa==fb)//已经出现过 确定了距离
			{
				if(dis[b]-dis[a]!=k)//先前的距离如果和现在不等 则矛盾
					cot++;
			}
			else
				Union(a,b,k);
			
		}
		printf("%d\n",cot);
	}
	return 0;
}