HDU 3038 How Many Answers Are Wrong

http://acm.hdu.edu.cn/showproblem.php?pid=3038

好牛的并查集

#include <cstdio>
#include <cstring>
using namespace std;

const int N=200010;
int set[N],sum[N];
int find(int x)
{
    if(x==set[x]) return x;
    int t=find(set[x]);
    sum[x]+=sum[set[x]];
    return set[x]=t;
}
int main()
{
    int n,m;
    while(~scanf("%d%d",&n,&m))
    {
        memset(sum,0,sizeof(sum));
        for(int i=0;i<=n;i++) set[i]=i;
        int cnt=0;
        while(m--)
        {
            int a,b,s;
            scanf("%d%d%d",&a,&b,&s); a--;
            int fa=find(a), fb=find(b);
            if(fa==fb)
            {
                if(sum[b]-sum[a]!=s) cnt++;
            }
            else
            {
                set[fb]=fa;
                sum[fb]=s+sum[a]-sum[b];
            }
        }
        printf("%d\n",cnt);
    }
    return 0;
}