带权并查集

#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
using namespace std;
const int maxn=2e5+7;
const int mod=1e9+7;
ll offe[maxn],boss[maxn];
int fin(int x){
    if(x==boss[x])return x;
    int z=boss[x];
    int y=fin(boss[x]);
    offe[x]+=offe[z];
    boss[x]=y;
    return y;
}
int main()
{
    int n,m,ans=0;
    while(scanf("%d %d",&n,&m)==2){
        ans=0;
        for(int i=0;i<=n;i++)boss[i]=i,offe[i]=0;
        for(int i=1;i<=m;i++){
            int l,r,x;
            scanf("%d %d %d",&l,&r,&x);
            l--;
            if(fin(l)==fin(r)){
                if(offe[l]-offe[r]!=x)ans++;
            }else{
                int fl=fin(l),fr=fin(r);
                boss[fl]=fr;
                offe[fl]=x-offe[l]+offe[r];
            }
        }
        printf("%d\n",ans);
    }
	return 0;
}