学步园

找最小路径是否有负环就好

#include<iostream>
#include<cstring>
using namespace std;
struct node
{
	int s,e,t;
};
node path[5201];
bool bellmanford(int s,int sw,int v,int e)
{
	bool flag;
	int weight[501],i;
	memset(weight,60,sizeof(weight));
	weight[s]=sw;
	while(v--)
	{
		flag=1;
		for(i=1;i<=e;i++)
		{
			if(weight[path[i].e]>weight[path[i].s]+path[i].t)
			{
				flag=0;
				weight[path[i].e]=weight[path[i].s]+path[i].t;
			}
		}
		if(flag)
		return 0;
	}
	return 1;
}
int main()
{
	int i,f,n,m,w;
	scanf("%d",&f);
	while(f--)
	{
		scanf("%d%d%d",&n,&m,&w);
		for(i=1;i<=2*m;i++)
		{
			scanf("%d%d%d",&path[i].s,&path[i].e,&path[i].t);
			i++;
			path[i].s=path[i-1].e;
			path[i].e=path[i-1].s;
			path[i].t=path[i-1].t;
		}
		for(;i<=2*m+w;i++)
		{
			scanf("%d%d%d",&path[i].s,&path[i].e,&path[i].t);
			path[i].t=-path[i].t;
		}
		if(bellmanford(1,0,n,i-1))
		{
			printf("YES\n");
		}
		else
		{
			printf("NO\n");
		}
	}
}