poj 3697 USTC campus network

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const int mod=10000007;int hash[mod];int getkey(int x){    int i=1,y=x;    y%=mod;    while(hash[y]!=-1&&hash[y]!=x)    {        y+=i*i;        i++;        if(y>=mod) y%=mod;    }    return y;}int stk[10005];bool vis[10005];int main(){    int n,m,ca=0;    while(scanf("%d%d",&n,&m),n,m)    {        memset(hash,-1,sizeof(hash));        memset(vis,false,sizeof(vis));        for(int i=0,a,b;i<m;i++)        { scanf("%d%d",&a,&b); a=a*10000+b; hash[getkey(a)]=a;        }        int f=0,r=1;        stk[0]=1;        vis[1]=true;        while(f!=r)        { int now=stk[f++]; for(int i=2;i<=n;i++) {     if(!vis[i]&&hash[getkey(now*10000+i)]==-1&&hash[getkey(i*10000+now)]==-1)     {         stk[r++]=i;         vis[i]=true;     } }        }        printf("Case %d: %dn",++ca,r-1);    }    return 0;}