CF1850H

 

带权并查集板题

 

维护到根的距离

#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>
#include <queue>
using namespace std;
const int N =2e5+10;
#define int long long
int n,fa[N],dis[N];
int find(int x){
	if(x==fa[x]) return x; 
	
	int t =find(fa[x]) ;
	dis[x]+=dis[fa[x]] ;
	fa[x]=t ;
	return fa[x] ;
}

void join(int x,int y,int v){
	int fx = find(x), fy= find(y) ;
	fa[fx] =fy ;
	dis[fx] = v+dis[y]-dis[x] ;
}
void sov(){
	int q ,flg=1;
	cin>>n>>q;
	for(int i=1;i<=n;i++) fa[i]=i,dis[i]=0 ;
	while(q--){
		int x,y,d ;
		cin>>x>>y>>d; 
		int fx =find(x), fy =find(y) ;
		if(fx==fy){
			if(d!=dis[x]-dis[y]) flg =0 ;
		}
		else{
			join(x,y,d);
		}
	}
	
	if(flg) cout<<"YES\n";else cout<<"NO\n" ;
}

signed main(){
	int T; cin>>T; while(T--) sov() ;
}