HDU3047 Zjnu Stadium 带权并查集

转：http://blog.csdn.net/shuangde800/article/details/7983965

#include <cstdio>
#include <cstring>
#include <queue>
#include <set>
#include <map>
#include <stack>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <cmath>
using namespace std;
const int N=2e5+5;
int n,m,fa[N],sum[N];
int find(int x)
{
    if(x==fa[x])return fa[x];
    int t=fa[x];
    fa[x]=find(fa[x]);
    sum[x]+=sum[t];
    return fa[x];
}
int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        for(int i=0; i<=n; ++i)fa[i]=i,sum[i]=0;
        int ans=0;
        while(m--)
        {
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            int x=find(u),y=find(v);
            if(x==y)
            {
                if(sum[v]-sum[u]!=w)++ans;
            }
            else if(x>y)
            {
                sum[x]=sum[v]-sum[u]-w;
                fa[x]=y;
            }
            else
            {
                sum[y]=sum[u]-sum[v]+w;
                fa[y]=x;
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}