八数码难题2.0

上次写完IDA*+曼哈顿，这次来一个双向BFS+map（别问我怎么那么多做法）

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
inline ll read() {
ll f=1,x=0;
char ch;
do {
ch=getchar();
if(ch=='-')f=-1;
} while(ch>'9'||ch<'0');
do {
x=x*10+ch-'0';
ch=getchar();
} while(ch>='0'&&ch<='9');
return f*x;
}
ll a,goal=123804765;
ll s[4][4];
map<int,int>dis;
map<int,int>vis;
int dx[5]={1,-1,0,0};
int dy[5]={0,0,1,-1};
inline void deque_BFS()
{
queue<ll>q;
if(a==goal){
cout<<"0\n";
exit(0);
}
vis[a]=1;vis[goal]=2;
dis[a]=0;dis[goal]=0;
q.push(a);
q.push(goal);
while(!q.empty())
{
ll now,cur=q.front();q.pop();
now=cur;
int sx,sy;
for(int i=3;i>=1;i--)
{
for(int j=3;j>=1;j--)
{
s[i][j]=now%10;now/=10;
if(!s[i][j])sx=i,sy=j;
}
}
for(int i=0;i<4;i++)
{
int xx=sx+dx[i],yy=sy+dy[i];
if(xx<1||xx>3||yy<1||yy>3) continue;
swap(s[sx][sy],s[xx][yy]);
now=0;
for(int j=1;j<=3;j++)
{
for(int k=1;k<=3;k++)
{
now=now*10+s[j][k];
}
}
if(vis[cur]==vis[now])
{
swap(s[sx][sy],s[xx][yy]);
continue;
}
if(vis[now]+vis[cur]==3)
{
cout<<dis[cur]+dis[now]+1<<endl;
exit(0);
}
dis[now]=dis[cur]+1;
vis[now]=vis[cur];
q.push(now);
swap(s[sx][sy],s[xx][yy]);
}
}
}
int main(){
freopen("eight.in","r",stdin);
freopen("eight.out","w",stdout);
a=read();
deque_BFS();
return 0;
}