poj 3259 bellman-ford判断是否存在负权回路

//
//  main.cpp
//  poj3259
//
//  Created by Fangpin on 15/5/28.
//  Copyright (c) 2015年 FangPin. All rights reserved.
//

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
using namespace std;
int g[600][600];
struct Edge{
    int from,to,dist;
};
int n,d[1000];
vector<Edge> vec;

bool bf(){
    for(int i=0;i<1000;++i)
        d[i]=10000000;
    d[1]=0;
    for(int i=0;i<n-1;++i){
        bool flag=false;
        for(int j=0;j<vec.size();++j){
            Edge &e=vec[j];
            if(d[e.to]>d[e.from]+e.dist){
                d[e.to]=d[e.from]+e.dist;
                flag=true;
            }
        }
        if(!flag) break;
    }
    for(int i=0;i<vec.size();++i){
        Edge &e=vec[i];
        if(d[e.to]>d[e.from]+e.dist)
            return false;
    }
    return true;
}
int main(int argc, const char * argv[]) {
    int t;
    cin>>t;
    while(t--){
        int m,k;
        vec.clear();
        cin>>n>>m>>k;
        memset(g,0,sizeof(g));
        for(int i=1;i<=m;++i){
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            Edge e;
            e.from=a;
            e.to=b;
            e.dist=c;
            vec.push_back(e);
            swap(e.from,e.to);
            vec.push_back(e);
        }
        for(int i=1;i<=k;++i){
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            c=-c;
            Edge e;
            e.from=a;
            e.to=b;
            e.dist=c;
            vec.push_back(e);
        }
        if(bf()) cout<<"NO\n";
        else cout<<"YES\n";
    }
    return 0;
}