Eight

Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 10351 Accepted Submission(s): 2755
Special Judge

Problem Description The 15-puzzle has been around for over 100 years; even if you don't know it by that name, you've seen it. It is constructed with 15 sliding tiles, each with a number from 1 to 15 on it, and all packed into a 4 by 4 frame with one tile missing. Let's call the missing tile 'x'; the object of the puzzle is to arrange the tiles so that they are ordered as:

 1  2  3  4
 5  6  7  8
 9 10 11 12
13 14 15  x

where the only legal operation is to exchange 'x' with one of the tiles with which it shares an edge. As an example, the following sequence of moves solves a slightly scrambled puzzle:

 1  2  3  4     1  2  3  4     1  2  3  4     1  2  3  4
 5  6  7  8     5  6  7  8     5  6  7  8     5  6  7  8
 9  x 10 12     9 10  x 12     9 10 11 12     9 10 11 12
13 14 11 15    13 14 11 15    13 14  x 15    13 14 15  x
            r->            d->            r->

The letters in the previous row indicate which neighbor of the 'x' tile is swapped with the 'x' tile at each step; legal values are 'r','l','u' and 'd', for right, left, up, and down, respectively.

Not all puzzles can be solved; in 1870, a man named Sam Loyd was famous for distributing an unsolvable version of the puzzle, and
frustrating many people. In fact, all you have to do to make a regular puzzle into an unsolvable one is to swap two tiles (not counting the missing 'x' tile, of course).

In this problem, you will write a program for solving the less well-known 8-puzzle, composed of tiles on a three by three
arrangement.

Input You will receive, several descriptions of configuration of the 8 puzzle. One description is just a list of the tiles in their initial positions, with the rows listed from top to bottom, and the tiles listed from left to right within a row, where the tiles are represented by numbers 1 to 8, plus 'x'. For example, this puzzle

1 2 3
x 4 6
7 5 8

is described by this list:

1 2 3 x 4 6 7 5 8

Output You will print to standard output either the word ``unsolvable'', if the puzzle has no solution, or a string consisting entirely of the letters 'r', 'l', 'u' and 'd' that describes a series of moves that produce a solution. The string should include no spaces and start at the beginning of the line. Do not print a blank line between cases.

Sample Input

2  3  4  1  5  x  7  6  8

Sample Output

ullddrurdllurdruldr

Source South Central USA 1998 (Sepcial Judge Module By JGShining)
Recommend JGShining | We have carefully selected several similar problems for you: 1044 1072 1180 1067 1401

题意：

就是还原八数码。输出操作。

思路：

利用康拓展开判重。通过康拓展开知一共有362879种状态。用逆序数判断可行解见八数码可行解。然后宽搜。

详细见代码：

#include
  
   
#include
   
     #include
    
      #include
     
       #include
      
        #include
       
         #include
        
          #include
         
           #include
          
            #include
           
             #include
             //#pragma comment(linker,"/STACK:1024000000,1024000000") using namespace std; const int INF=0x3f3f3f3f; const double eps=1e-8; const double PI=acos(-1.0); const int maxn=370010;//最大为362879 const int num=9; const int over=46233; typedef __int64 ll; int c[10],head,tail; int vis[maxn]; int fac[15]={1,1,2,6,24,120,720,5040,40320,362880,3628800,39916800,479001600};//存阶乘 int dx[4]={-1,1,-3,3};//四个方向 map
             
               mpp; struct yb { int mp[10]; int bp,pre,code,dre;//空格位置。上一状态的下标(记录路径),康拓展开,方向。 } q[maxn],tp,tt; /***********树状数组求逆序数(规模比较小快不了多少)***********/ int lowbit(int x) { return x&-x; } void update(int x) { while(x<=num) { c[x]++; x+=lowbit(x); } } int getsum(int x) { int sum=0; while(x>0) { sum+=c[x]; x-=lowbit(x); } return sum; } /***************康拓展开***************/ ll contor(int arr[]) { int i,j,ct; ll sum=0; for(i=0;i
              
               =num) return false; if(dre>1) return true; if(x>lim||x

hdu 1043 poj 1077 Eight Time （搜索&八数码）(一)

Eight