POJ--3259 Wormholes （SPFA判负环）

题目电波   3259 Wormholes

#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#include<stdio.h>
using namespace std;
#define maxn 100010
#define inf 0x3f3f3f3f
struct ac{
  int to,va;
  ac(){}
  ac(int a,int b){
    to=a,va=b;
  }
};
vector<ac>q[maxn];
int dis[maxn],vis[maxn];
bool fa[maxn];
int n,m,s;
void init(){
   for(int j=1;j<=maxn;j++) q[j].clear();
}
bool spfa(){
   memset(vis,0,sizeof(vis));
   memset(fa,0,sizeof(fa));
   memset(dis,inf,sizeof(dis));
   dis[1]=0;
   queue<int>pq;
   pq.push(1);
   while(!pq.empty()){
      int u=pq.front();
      pq.pop();
      fa[u]=0;
      for(int j=0;j<q[u].size();j++){
         int v=q[u][j].to;
         int va=q[u][j].va;
         if(dis[v]>dis[u]+va){
            dis[v]=dis[u]+va;
            if(!fa[v]){
               fa[v]=1;
               vis[v]++;
               pq.push(v);
               if(vis[v]>=n){
                 return 1;
               }
            }
         }
      }
   }
   return 0;
}
int main(){
   int t;
   cin>>t;
   while(t--){
    init();
     cin>>n>>m>>s;
     for(int j=0;j<m;j++){
        int u,v,va;
        scanf("%d%d%d",&u,&v,&va);
        q[u].push_back(ac(v,va));
        q[v].push_back(ac(u,va));
     }
     for(int j=0;j<s;j++){
        int u,v,va;
        scanf("%d%d%d",&u,&v,&va);
        q[u].push_back(ac(v,-va));
     }
     if(spfa()){
        cout<<"YES"<<endl;
     }else{
        cout<<"NO"<<endl;
     }
   }
}