八数码问题（紫薯P199）

#include <algorithm>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <set>
using namespace std;
typedef int State[];
const int maxstate = ;
State st[maxstate], goal;
int dist[maxstate];
const int dx[] = {-, , , };
const int dy[] = {, , -, };
set<int> vis;
/*
void init_lookup_table()
{
    vis.clear();
}
int try_to_insert(int s)
{
    int v = 0;
    for(int i = 0; i < 9; i++)
        v = v * 10 + st[s][i];
    if(vis.count(v))
        return 0;
    vis.insert(v);
    return 1;
}
*/
const int hashsize = ;
int head[hashsize], Next[maxstate];
void init_lookup_table()
{
    memset(head, , sizeof(head));
}
int Hash(State &s)
{
    int v = ;
    for(int i = ; i < ; i++)
        v = v *  + s[i];
    return v % hashsize;
}
int try_to_insert(int s)
{
    int h = Hash(st[s]);
    int u = head[h];
    while(u)
    {
        if(memcmp(st[u], st[s], sizeof(st[s])) == )
            return ;
        u = Next[u];
    }
    Next[s] = head[h];
    head[h] = s;
    return ;
}
int bfs()
{
    init_lookup_table();
    int first = , last = ;
    dist[] = ;
    while(first < last)
    {
        State &s = st[first];
        if(memcmp(goal, s, sizeof(s)) == )
            return first;
        int z;
        for(z = ; z < ; z++)
            if(s[z] == )
                break;
        int x = z / ;
        int y = z % ;
        for(int i = ; i < ; i++)
        {
            int fx = x + dx[i];
            int fy = y + dy[i];
            int fz = fx *  + fy;
            if(fx >=  && fy >=  && fx <  && fy < )
            {
                State &t = st[last];
                memcpy(&t, &s, sizeof(s));
                t[fz] = s[z];
                t[z] = s[fz];
                dist[last] = dist[first] + ;
                if(try_to_insert(last))
                    last++;
            }
        }
        first++;
    }
    return ;
}
int main()
{
    for(int i = ; i < ; i++)
        scanf("%d", &st[][i]);
    for(int i = ; i < ; i++)
        scanf("%d", &goal[i]);
    int ans = bfs();
    if(ans > )
        printf("%d\n", dist[ans]);
    else
        printf("-1\n");
    return ;
}
/*
2 6 4 1 3 7 0 5 8
8 1 5 7 3 6 4 0 2
*/