八数码问题

#include<stdio.h>
#include<string.h>
#include<set>
#include<time.h>
using namespace std;

typedef int state[9];
const int max=1000000;
state st[max],goal;
int dist[max];
const int dx[]={-1,1,0,0};
const int dy[]={0,0,-1,1};

struct cmp
{
    bool operator ()(int a,int b)const
    {
        return memcmp(&st[a],&st[b],sizeof(st[b]))<0;
    }
};

set<int, cmp> vis;

void in()
{
    vis.clear();
}

int insert(int s)
{
    if(vis.count(s)) return 0;
    vis.insert(s);
    return 1;
}

int bfs()
{
    int front,rear,z,d,newy,newz,newx,x,y;
    rear=2;
    front=1;
    //state s,t;
    in();
    while(front<rear)
    {
        state &s=st[front];
        if(memcmp(goal,s,sizeof(s))==0) return front;
        for(z=0;z<9;z++) if(!s[z]) break;
        x=z/3;y=z%3;
        for(d=0;d<4;d++)
        {
             newx=x+dx[d];
             newy=y+dy[d];
             newz=newx*3+newy;
             if(newx>=0&&newx<3&&newy>=0&&newy<3)
             {
                state &t=st[rear];
                 memcpy(&t,&s,sizeof(s));
                 t[newz]=s[z];
                 t[z]=s[newz];
                 dist[rear]=dist[front]+1;
                 if(insert(rear)) rear++;
             }
        }
        front++;
    }
    return 0;
}
        
int main()
{
    int i,ans;
    for(i=0;i<9;i++) scanf("%d",&st[1][i]);
    for(i=0;i<9;i++) scanf("%d",&goal[i]);
    ans=bfs();
    if(ans>0) printf("%d\n",dist[ans]);
    else printf("-1\n");
    printf("%d\n",clock()/CLOCKS_PER_SEC);
    return 0;
}