用spfa 判负环

#include<stdio.h>
#include<cstring>
#include<queue>
#include<algorithm>
using namespace std;

struct my{
  int v;
  int next;
  int dist;
};

int m,n;
const int maxn=100000;
my bian[maxn];
int adj[maxn];
int fa;
bool vis[maxn];
int d[maxn];
int cnt[maxn];

void myinsert(int u,int v,int zhi){
    bian[++fa].v=v;
    bian[fa].dist=zhi;
    bian[fa].next=adj[u];
    adj[u]=fa;
}

bool spfa(){
     queue<int>q;
     for (int i=1;i<=n;i++){
        q.push(i);
        d[i]=0;
     }
     vis[1]=true;
     while(!q.empty()){
        int u=q.front();
            q.pop();
            vis[u]=false;
        for (int i=adj[u];i!=-1;i=bian[i].next){
            if(d[bian[i].v]>d[u]+bian[i].dist){
                d[bian[i].v]=d[u]+bian[i].dist;
                if(!vis[bian[i].v]){
                    q.push(bian[i].v);
                    vis[bian[i].v]=true;
                    if(++cnt[bian[i].v]>n) return true;
                }
            }
        }
     }
    return false;
}
int main(){
    memset(bian,-1,sizeof(bian));
    memset(adj,-1,sizeof(adj));
   scanf("%d%d",&n,&m);
   int u,v,zhi;
   for (int i=1;i<=m;i++){
    scanf("%d%d%d",&u,&v,&zhi);
    myinsert(u,v,zhi);
    myinsert(v,u,zhi);
   }
  if( spfa()) printf("yes\n");
  else printf("no\n");

return 0;
}