1 package study_code;
  2 
  3 import java.util.LinkedList;
  4 import java.util.Queue;
  5 import java.util.Scanner;
  6 
  7 public class 八数码 {
  8     
  9     static int[] vis = new int [900900]; //判断哈希值是否被访问
 10     static int[] f = new int[9];    //保存阶乘
 11     static int end; //最终状态的哈希值
 12     static node start = new node(); 
 13     static String resPath;
 14     static int[][] dir = {{-1,0},{1,0},{0,-1},{0,1}};
 15     static char[] dirc = {‘U‘,‘D‘,‘L‘,‘R‘};
 16     static class node{
 17         int loc; //记录当前空格位置 用一个数字记录 1-9
 18         int s[]; //记录当前所有数字的位置
 19         int hashVal; //当前状态的哈希值
 20         String path = ""; //记录当前路径
 21         public node() {
 22         }
 23     }
 24     
 25     public static void fac() {
 26         f[0] = 1;
 27         for (int i = 1; i < f.length; i++) {
 28             f[i] = f[i-1] * i;
 29         }
 30     }
 31     
 32     //康拓展开
 33     public static int getHash(int[] s) {
 34         int res = 0;
 35         for (int i = 0; i < s.length; i++) {
 36             int index =0;
 37             for (int j = i+1; j < s.length; j++) {
 38                 if (s[j]<s[i]) {
 39                     index++;
 40                 }
 41             }
 42             res += index*f[9-1-i];
 43         }
 44         return res;        
 45     }
 46     
 47     
 48     public static boolean bfs() {
 49         Queue<node> q = new LinkedList<node>();
 50         q.offer(start);
 51         vis[start.hashVal] = 1;
 52         while (!q.isEmpty()) {
 53             node cur = q.poll();
 54             vis[cur.hashVal] = 1;
 55             if (cur.hashVal == end) {
 56                 resPath = cur.path;
 57                 return true;
 58             }
 59             int x =cur.loc/3;
 60             int y =cur.loc%3;
 61             for (int i = 0; i < 4; i++) {
 62                 int tx = x + dir[i][0];
 63                 int ty = y + dir[i][1];
 64                 if (tx<0||ty<0||tx>=3||ty>=3) {
 65                     continue;
 66                 }
 67                 node temp = new node();
 68                 temp.loc = tx*3+ty;
 69                 temp.path = cur.path+dirc[i];
 70                 temp.s = cur.s.clone();
 71                 //交换空格的位置
 72                 temp.s[cur.loc] = temp.s[temp.loc];
 73                 temp.s[temp.loc] = 0;
 74                 
 75                 temp.hashVal = getHash(temp.s);
 76                 if (vis[temp.hashVal] == 1) {
 77                     continue;
 78                 }
 79                 q.offer(temp);
 80                 vis[temp.hashVal] = 1;
 81             }
 82         }
 83         return false;
 84         
 85         
 86         
 87     }
 88     public static void main(String[] args) {
 89         Scanner sc = new Scanner(System.in);
 90         fac();
 91         String t = sc.nextLine();
 92         char[] c = t.toCharArray();
 93         int[] n = new int[c.length];
 94         for (int i = 0; i < c.length; i++) {
 95             if (c[i] == ‘.‘) {
 96                 n[i] = 0;
 97                 start.loc = i;
 98             }else {
 99                 n[i] = c[i] - ‘0‘;
100             }
101         }
102         start.s = n.clone();
103         start.hashVal = getHash(start.s);
104         t = sc.nextLine();
105         c = t.toCharArray();
106         n = new int[c.length];
107         for (int i = 0; i < c.length; i++) {
108             if (c[i] == ‘.‘) {
109                 n[i] = 0;
110             }else {
111                 n[i] = c[i] - ‘0‘;
112             }
113         }
114         end = getHash(n);
115         bfs();
116         System.out.println(resPath.length());
117     }
118 }