CODEVS2645 Spore

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int next[20001]={0},point[10001]={0},en[20001]={0},va[20001]={0},que[2010]={0},num[10001]={0};
long long dis[1001]={0};
bool visit[10001]={false};
int main()
{
    int n,m,i,j,tot,head,tail,g1,g2,c1,c2,x,y;
    long long maxn;
    bool ff;
    maxn=2100000000;
    while(true)
    {
        tot=0;
        memset(que,0,sizeof(que));
        memset(next,0,sizeof(next));
        memset(point,0,sizeof(point));
        memset(en,0,sizeof(en));
        memset(va,0,sizeof(va));
        memset(num,0,sizeof(num));
        memset(visit,false,sizeof(visit));
        ff=false;
        scanf("%d%d",&n,&m);
        if (n==0&&m==0) break;
        if (m==0&&n==1) 
        {
          printf("0\n");
          continue;
        }
        if (m==0)
        {
            printf("No such path\n");
            continue;
        }
        for (i=1;i<=m;++i)
        {
            scanf("%d%d%d%d",&g1,&g2,&c1,&c2);
            ++tot;
            next[tot]=point[g1];
            point[g1]=tot;
            en[tot]=g2;
            va[tot]=c1;
            ++tot;
            next[tot]=point[g2];
            point[g2]=tot;
            en[tot]=g1;
            va[tot]=c2;
        }
        head=0;tail=1;que[tail]=1;
        for (i=0;i<=n;++i)
          dis[i]=maxn;
        dis[1]=0;
        visit[1]=true;
        num[1]++;
        do
        {
            ++head;
            head=(head-1)%2000+1;    
            x=que[head];
            visit[x]=false;
             y=point[x];
             while(y!=0)
            {
                if (dis[en[y]]>dis[x]+va[y])
                {
                    dis[en[y]]=dis[x]+va[y];
                    if (!visit[en[y]])
                    {
                        ++tail;
                        tail=(tail-1)%2000+1;
                        que[tail]=en[y];
                        ++num[en[y]];
                        visit[en[y]]=true;
                        if (num[en[y]]>n)
                        {
                            ff=true;
                            break;
                        }
                    }
                }
                y=next[y];
            }
            if (ff) break;
        }while(head!=tail);
        if (ff) printf("No such path\n");
        else
        {
          if (dis[n]!=maxn) printf("%lld\n",dis[n]);
          else printf("No such path\n");
        }
    }
}