#include <stdio.h>
#include <stdlib.h>
#include <string.h>
const int hashsize=70001;
const int maxnode=50000;
const int maxp=40;
const int ten[]={1,10,100,1000,10000,100000,1000000,10000000,100000000};
const int C[]={2,3,2,3,4,3,2,3,2};
const int EP[][4]={{1,3,0,0},{0,2,4,0},{1,5,0,0},{0,4,6,0},{1,3,5,7},{2,4,8,0},{3,7,0,0},{4,6,8,0},{5,7,0,0}};
struct Tlist
{
int data,d;
Tlist *next;
};
struct Thashpoint
{
int data;
Thashpoint *next;
};
//Memory
int ID;
Tlist listM[maxnode],*q;
Thashpoint hashM[maxnode],*p;
//data
int src,dest;
//heap
Tlist *head[maxp],*expand[maxp],*lp1,*lp2;
//Hash
Thashpoint *hash[hashsize];
//expand
int nowp,A[9],arcT[9],dist[9][9],b,depth,swap[9][9];
int data,G,newdata,newG;
bool find_answer;
void readdata(const char *filename,int &data)
{
int i,v;
FILE *f=fopen(filename,"r");
data=0;
for (i=0;i<9;i++)
{
fscanf(f,"%d",&v);
data=data+v*ten[i];
}
fclose(f);
}
bool check_noanswer()
{
int p[9],i,b1,b2;
bool vis[9];
for (i=0;i<9;i++)
p[i]=arcT[src/ten[i]%10];
for (b1=0; src/ten[b1]%10!=0;b1++);
for (b2=0;dest/ten[b2]%10!=0;b2++);
int countP=0;
memset(vis,false,sizeof(vis));
for (i=0;i<9;i++)
if (!vis[i])
{
countP++;
for (int k=i;!vis[k];k=p[k])
vis[k]=true;
}
return (countP-dist[b1][b2])%2==0;
}
void preprocess()
{
ID=0;
find_answer=false;
memset(hash,0,sizeof(hash));
memset(head,0,sizeof(head));
memset(expand,0,sizeof(expand));
for (int k=0;k<9;k++)
arcT[dest/ten[k]%10]=k;
for (int u=0;u<9;u++)
for (int v=0;v<9;v++)
{
dist[u][v]=abs(u/3-v/3)+abs(u%3-v%3);
swap[u][v]=ten[u]-ten[v];
}
}
void addnode()
{
if (newdata==dest)
{
printf("%d\n",depth);
find_answer=true;
return;
}
int address=newdata%hashsize;
for (p=hash[address];p!=NULL;p=p->next)
if (p->data==newdata)
return;
if (ID==maxnode)
return;
p=&hashM[ID];
p->data=newdata;
p->next=hash[address];
hash[address]=p;
q=&listM[ID];
ID++;
q->data=newdata;
q->d=depth;
if (newG>=maxp)
return;
if (newG==nowp)
{
q->next=expand[depth];
expand[depth]=q;
}
else
{
q->next=head[newG];
head[newG]=q;
}
}
void solve()
{
nowp=-1;
newdata=src;
newG=0;
for (int k=0;k<9;k++)
if (src/ten[k]%10!=0)
newG+=dist[arcT[src/ten[k]%10]][k];
depth=0;
addnode();
if (find_answer)
return;
for (int p=0;p<maxp;p++) if (head[p]!=NULL)
{
nowp=p;
for (lp1=head[p];lp1!=NULL;lp1=lp2)
{
lp2=lp1->next;
lp1->next=expand[lp1->d];
expand[lp1->d]=lp1;
}
for (int d=0;d<=p;d++)
for (;expand[d]!=NULL;)
{
data=expand[d]->data;
G=p-expand[d]->d;
depth=expand[d]->d+1;
expand[d]->d=-2;
expand[d]=expand[d]->next;
for (b=0;data/ten[b]%10!=0;b++);
for (int v=0;v<C[b];v++)
{
int u=EP[b][v];
int c=data/ten[u]%10;
newdata=data+swap[b][u]*c;
c=arcT[c];
newG=depth+G-dist[c][u]+dist[c][b];
addnode();
if (find_answer)
return;
}
}
}
printf("-1\n");
}
int main()
{
readdata("start.txt",src);
readdata("goal.txt",dest);
preprocess();
if (check_noanswer())
printf("-1\n");
else
solve();
return 0;
}