3038(HDU)

#include<iostream>
#include<cstdio>
#include<string.h>
#include<cstring>
#include<string>
#include<stack>
#include<set>
#include<algorithm>
#include<cmath>
#include<vector>
#include<map>

#define LOCAL
#define ll long long
#define lll unsigned long long
#define MAX 1000009
#define eps 1e-8
#define INF 0x7fffffff
#define mod 1000000007

using namespace std;
/*

PS:http://blog.youkuaiyun.com/acm_cxlove/article/details/8086806

题意：

想法：反过来求，不是0是根节点！！

*/
int sum[MAX];//到根节点的距离
int father[MAX];
int n,m;

int find(int x)
{
   if(father[x]!=x)
   {
       int t = father[x];
       father[x] = find(t);
       sum[x]+=sum[t];//回溯下
   }
   return father[x];
}
void init(int n)
{
    for(int i = 0; i<=n; i++)
    {
        father[i] = i;
        sum[i] = 0;
    }
}
int main()
{
   // freopen("date.txt","r",stdin);
    int n,m;
    int u,v,w;
    int ans;
    while(~scanf("%d%d",&n,&m))
    {
        ans = 0;
        init(n);
        for(int i = 0; i<m; i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            u--;
            int xx = find(u);
            int yy = find(v);
            if(xx==yy)
            {
                if(sum[u] - sum[v]!=w)
                {
                    ans++;
                }
            }
            else
            {
                father[xx] = yy;
                sum[xx] = sum[v] + w - sum[u];//xx到yy的距离,画图就知道了。
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}