hdu 2918(IDA*)

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2918

思路：这道题与前面几道类似，可以说是被秒杀了！！！构造启发式函数h()=(cnt+3)/4(cnt为不在位的点的个数)。

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;

 int map[][];
 char str[];
 int max_deep;

 int Get_H()
 {
     int cnt=;
     for(int i=;i<=;i++)
         for(int j=;j<=;j++)
             if(map[i][j]!=(i-)*+j)cnt++;
     return (cnt+)/;
 }

 void MoveL_A()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveR_A()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveL_B()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveR_B()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveL_C()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveR_C()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveL_D()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 void MoveR_D()
 {
     int tmp=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=map[][];
     map[][]=tmp;
 }

 bool IDA_star(int deep)
 {
     if(Get_H()+deep>max_deep)return false;
     if(deep==max_deep)return true;

     MoveL_A();
     if(IDA_star(deep+))return true;
     MoveR_A();

     MoveR_A();
     if(IDA_star(deep+))return true;
     MoveL_A();

     MoveL_B();
     if(IDA_star(deep+))return true;
     MoveR_B();

     MoveR_B();
     if(IDA_star(deep+))return true;
     MoveL_B();

     MoveL_C();
     if(IDA_star(deep+))return true;
     MoveR_C();

     MoveR_C();
     if(IDA_star(deep+))return true;
     MoveL_C();

     MoveL_D();
     if(IDA_star(deep+))return true;
     MoveR_D();

     MoveR_D();
     if(IDA_star(deep+))return true;
     MoveL_D();
     return false;
 }

 int main()
 {
     int n,t=;
     while(~scanf("%s",str)){
         if(strcmp(str,"")==)break;
         n=str[]-'';
         for(int j=,i=;i<=;j++,i++){
             map[(i-)/+][j]=str[i]-'';
             if(i%==)j=;
         }
         /*
         for(int i=1;i<=3;i++){
             for(int j=1;j<=3;j++){
                 printf("%d ",map[i][j]);
             }
             printf("\n");
         }*/
         if(Get_H()==){
             printf("%d. 0\n",t++);
             continue;
         }
         for(max_deep=;max_deep<=n;max_deep++){
             if(IDA_star())break;
         }
         if(max_deep>n){
             printf("%d. -1\n",t++);
         }else
             printf("%d. %d\n",t++,max_deep);
     }
     return ;
 }