IOI1994 Beijing 2008 's Wall clock iteration deepened

Generally speaking, this is a very ⑨ problem, because:

(1) ⑨ a wall clock in the title

(2) There are ⑨ kinds of operation scheme

(3) This problem because the solution space is too small, can directly ⑨ heavy cycle!!

This problem can be solved efficiently with iterative deepening search, and the pruning strategy is also obvious:

The sequence of operations required by > must be monotonous and non-diminishing.

> The same operation cannot occur 4 times or more in the solution (Operation 4 times equals no operation)

Code:

1#include <cstdio>2#include <cstring>3#include <algorithm>4 5 using namespacestd;6 7 intdir[Ten]={0};8 intcmdcnt[Ten]={0};9 intans[Ten]={0};Ten  One voidMoveint_cmd) A { -++Cmdcnt[_cmd]; -      the     Switch(_cmd) -     { -      Case 1: ++dir[1]; ++dir[2]; ++dir[4]; ++dir[5]; Break; -      Case 2: ++dir[1]; ++dir[2]; ++dir[3]; Break; +      Case 3: ++dir[2]; ++dir[3]; ++dir[5]; ++dir[6]; Break; -      Case 4: ++dir[1]; ++dir[4]; ++dir[7]; Break; +      Case 5: ++dir[2]; ++dir[4]; ++dir[5]; ++dir[6]; ++dir[8]; Break; A      Case 6: ++dir[3]; ++dir[6]; ++dir[9]; Break; at      Case 7: ++dir[4]; ++dir[5]; ++dir[7]; ++dir[8]; Break; -      Case 8: ++dir[7]; ++dir[8]; ++dir[9]; Break; -      Case 9: ++dir[5]; ++dir[6]; ++dir[8]; ++dir[9]; Break; -     } - } -  in voidUndoint_cmd) - { to--Cmdcnt[_cmd]; +      -     Switch(_cmd) the     { *      Case 1:--dir[1]; --dir[2]; --dir[4]; --dir[5]; Break; $      Case 2:--dir[1]; --dir[2]; --dir[3]; Break;Panax Notoginseng      Case 3:--dir[2]; --dir[3]; --dir[5]; --dir[6]; Break; -      Case 4:--dir[1]; --dir[4]; --dir[7]; Break; the      Case 5:--dir[2]; --dir[4]; --dir[5]; --dir[6]; --dir[8]; Break; +      Case 6:--dir[3]; --dir[6]; --dir[9]; Break; A      Case 7:--dir[4]; --dir[5]; --dir[7]; --dir[8]; Break; the      Case 8:--dir[7]; --dir[8]; --dir[9]; Break; +      Case 9:--dir[5]; --dir[6]; --dir[8]; --dir[9]; Break; -     } $ } $  -InlineBOOLisdest () - { the      for(intI=1; i<=9; i++)if(Dir[i] &3)return false; -     return true;Wuyi } the  - BOOLSearch_aux (int_maxdepth,int_curdepth,int_lastcmd) Wu { -     if(Isdest ())return true; About     if(_curdepth > _maxdepth)return false; $  -      for(inti=_lastcmd;i<=9; i++) -     { -         if(Cmdcnt[i] <3) A         { + move (i); the             BOOLNext=search_aux (_maxdepth,_curdepth+1, i); - undo (i); $             if(next) {++ans[i];return true; } the         } the     } the      the     return false; - } in  the voidinput () the { About      for(intI=1; i<=9; i++) scanf ("%d", dir+i); the } the  the voidSearch () + { -      for(intI=1;; i++)if(Search_aux (I,1,1))return; the }Bayi  the voidPrintans () the { -      for(intI=1; i<=9; i++)  -          while(ans[i]--) printf ("%d", i); the } the  the intMain () the { - input (); the search (); the Printans (); the     return 0;94}

Cirno is willing to try this problem (*^__^*)

IOI1994 Beijing 2008 's Wall clock iteration deepened