BFS!
#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
typedef long long ll;
int ans = 123456780;
const int P = 1e6 + 7;
vector<int>v[P + 5];
int n;
int fx[] = { 1,-1,0,0 };
int fy[] = { 0,0,1,-1 };
bool find(int x)
{
int y = x % P;
for (int i = 0; i < v[y].size(); i++)
{
if (v[y][i] == x)
return true;
}
return false;
}
struct node
{
int val;
int step;
};
void bfs()
{
queue<node>q;
q.push({ n,0 });
while (!q.empty())
{
node u = q.front();
q.pop();
if (u.val == ans)
{
cout << u.step;
return;
}
//狀態轉移
int a[5][5];
int x = u.val;
int kx, ky;
for (int i = 3; i >= 1; i--)
{
for (int j = 3; j >= 1; j--)
{
a[i][j] = x % 10;
x /= 10;
if (a[i][j] == 0)kx = i, ky = j;
}
}
int b[5][5];
for (int i = 0; i < 4; i++)
{
memcpy(b, a, sizeof(a));
int nx = kx + fx[i];
int ny = ky + fy[i];
if (nx > 3 || ny > 3 || nx < 1 || ny < 1)
continue;
swap(b[nx][ny], b[kx][ky]);
int nownum=0;
for (int i = 1; i <= 3; i++)
{
for (int j = 1; j <= 3; j++)
{
nownum *= 10;
nownum += b[i][j];
}
}
if (find(nownum))
continue;
v[nownum % P].push_back(nownum);
q.push({ nownum,u.step + 1 });
}
}
cout << -1;
return;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
for (int i = 1; i <= 9; i++)
{
char x;
cin >> x;
n *= 10;
if (x == 'x')
{
n += 0;
}
else
{
n += x - '0';
}
}
v[n % P].push_back(n);
bfs();
return 0;
}