> #include<iostream>
> #include<cstdio>
> #include<cmath>
> #include<algorithm>
> #include<vector>
> #include<queue>
> #include<cstring>
> using namespace std;
> #define M 5205 //ac
> //#define M 3000 runtime error
> //#define M 5000 wrong answer
> #define N 505
> 
> struct node {
> 	int p,next,dis;
> } g[M];
> int n,m,w,cnt[N],inq[N],head[N],dis[N],k;
> 
> void addEdge(int s,int d,int dist) {
> 	g[k].p=d;
> 	g[k].dis=dist;
> 	g[k].next=head[s];
> 	head[s]=k++;
> }
> bool spfa(int s) {
> 	memset(dis,0x3f3f3f3f,sizeof(dis));
> 	memset(inq,0,sizeof(inq));
> 	memset(cnt,0,sizeof(cnt));
> 	queue<int> q;
> 	q.push(s);
> 	cnt[s]=1;
> 	inq[s]=1;
> 	while(!q.empty()) {
> 		int t=q.front();
> 		q.pop();
> 		inq[t]=0;
> 		for(int i=head[t],p; i!=-1; i=g[i].next) {
> 			p=g[i].p;
> 			if(dis[p]>dis[t]+g[i].dis) {
> 				dis[p]=dis[t]+g[i].dis;
> 				if(!inq[p]) {
> 					q.push(p);
> 					inq[p]=1;
> 					if(++cnt[p]>n)
> 						return true;
> 				}
> 			}
> 		}
> 	}
> 	return false;
> }
> int main() {
> 	freopen("in.txt","r",stdin);
> 	int f;
> 	cin>>f;
> 	while(f--) {
> 		cin>>n>>m>>w;
> 		memset(head,-1,sizeof(head));
> 		k=0;
> 		for(int i=0,a,b,d; i<m; i++) {
> 			scanf("%d%d%d",&a,&b,&d);
> 			addEdge(a,b,d);
> 			addEdge(b,a,d);
> 		}
> 		for(int i=0,a,b,d; i<w; i++) {
> 			scanf("%d%d%d",&a,&b,&d);
> 			addEdge(a,b,-d);
> 		}
> 		int ok=0;
> 		for(int i=1; i<=n; i++) {
> 			if(spfa(i)) {
> 				ok=1;
> 				break;
> 			}
> 		}
> 		if(ok)
> 			cout<<"YES\n";
> 		else
> 			cout<<"NO\n";
> 	}
> 	return 0;
> }
懂了。。