Wormholes POJ

//判断负环     dist初始化为正无穷
//正环  负无穷 
#include<iostream>
#include<cstring>
#include<queue>
#include<algorithm>
using namespace std;
const int N = 510, M = 5210;
int dist[N];
int h[N], e[M], w[M], ne[M], idx;
int n,m,z;
void add(int a,int b,int c)
{
    e[idx]=b;
    w[idx]=c;
    ne[idx]=h[a];
    h[a]=idx++;
}
bool st[N];
int times[N];
bool spfa()
{
    memset(st,0,sizeof st);
    memset(times,0,sizeof times);
    queue<int>q;
    for(int i=1;i<=n;i++)
    {
        q.push(i);
        st[i]=1;
        times[i]++;
    }
    while(q.size())
    {
        int t=q.front();
        q.pop();
        st[t]=0;
        for(int i=h[t];~i;i=ne[i])
        {
            int j=e[i];
            if(dist[j]>dist[t]+w[i])
            {
                dist[j]=dist[t]+w[i];
                if(!st[j])
                {
                    st[j]=1;
                    q.push(j);
                    times[j]++;
                    if(times[j]>n)
                        return true;
                }
            }
        }
    }
    return false;
}
int main()
{
    int t,a,b,c;
    cin>>t;
    while(t--)
    {
        cin>>n>>m>>z;
        idx=0;
        memset(h,-1,sizeof h);
        memset(dist,0x3f,sizeof dist);
        for(int i=1;i<=m;i++)
        {
            int a,b,c;
            cin>>a>>b>>c;
            add(a,b,c);
            add(b,a,c);
        }
        for(int i=1;i<=z;i++)
        {
            int a,b,c;
            cin>>a>>b>>c;
            add(a,b,-c);
        }
        if(spfa())
            cout<<"YES"<<endl;
        else
            cout<<"NO"<<endl;
    }
    return 0;
}