求负环自然要用 belllman

#include 
    
     #include 
     
      int F,n,m,w,p,dist[501];structnode{
        int s,e,t;}grid[5500];int bellman(){
        int i,k;    memset (dist,0,sizeof (dist));    for (k=1;k<=n-1;k++)        for(i=1;i<=p;i++)            if (dist[ grid[i].s ]> dist[ grid[i].e ]+grid[i].t)            dist[ grid[i].s ]=dist[ grid[i].e ]+grid[i].t;    for (i=1;i<=p;i++)        if (dist[ grid[i].s ]> dist[ grid[i].e ]+grid[i].t)        return 1;    return 0;}int main(){
        int s,e,t;    scanf("%d",&F);    while (F--)    {
            p=1;        memset(grid,0,sizeof(grid));        scanf("%d%d%d",&n,&m,&w);        while(m--)        {
                scanf("%d%d%d",&s,&e,&t);            grid[p].s=s;grid[p].e=e;grid[p++].t=t;            grid[p].s=e;grid[p].e=s;grid[p++].t=t;        }        while(w--)        {
                scanf("%d%d%d",&s,&e,&t);            grid[p].s=s;grid[p].e=e;grid[p++].t=-t;        }        printf("%s\n",bellman()?"YES":"NO");    }	return 0;}