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[4][4];
char str[14];
int max_deep;

int Get_H()
{
    int cnt=0;
    for(int i=1;i<=3;i++)
        for(int j=1;j<=3;j++)
            if(map[i][j]!=(i-1)*3+j)cnt++;
    return (cnt+3)/4;
}

void MoveL_A()
{
    int tmp=map[1][1];
    map[1][1]=map[1][2];
    map[1][2]=map[2][2];
    map[2][2]=map[2][1];
    map[2][1]=tmp;
}

void MoveR_A()
{
    int tmp=map[1][1];
    map[1][1]=map[2][1];
    map[2][1]=map[2][2];
    map[2][2]=map[1][2];
    map[1][2]=tmp;
}

void MoveL_B()
{
    int tmp=map[1][2];
    map[1][2]=map[1][3];
    map[1][3]=map[2][3];
    map[2][3]=map[2][2];
    map[2][2]=tmp;
}

void MoveR_B()
{
    int tmp=map[1][2];
    map[1][2]=map[2][2];
    map[2][2]=map[2][3];
    map[2][3]=map[1][3];
    map[1][3]=tmp;
}

void MoveL_C()
{
    int tmp=map[2][1];
    map[2][1]=map[2][2];
    map[2][2]=map[3][2];
    map[3][2]=map[3][1];
    map[3][1]=tmp;
}

void MoveR_C()
{
    int tmp=map[2][1];
    map[2][1]=map[3][1];
    map[3][1]=map[3][2];
    map[3][2]=map[2][2];
    map[2][2]=tmp;
}

void MoveL_D()
{
    int tmp=map[2][2];
    map[2][2]=map[2][3];
    map[2][3]=map[3][3];
    map[3][3]=map[3][2];
    map[3][2]=tmp;
}

void MoveR_D()
{
    int tmp=map[2][2];
    map[2][2]=map[3][2];
    map[3][2]=map[3][3];
    map[3][3]=map[2][3];
    map[2][3]=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+1))return true;
    MoveR_A();

    MoveR_A();
    if(IDA_star(deep+1))return true;
    MoveL_A();

    MoveL_B();
    if(IDA_star(deep+1))return true;
    MoveR_B();
    
    MoveR_B();
    if(IDA_star(deep+1))return true;
    MoveL_B();

    MoveL_C();
    if(IDA_star(deep+1))return true;
    MoveR_C();

    MoveR_C();
    if(IDA_star(deep+1))return true;
    MoveL_C();

    MoveL_D();
    if(IDA_star(deep+1))return true;
    MoveR_D();

    MoveR_D();
    if(IDA_star(deep+1))return true;
    MoveL_D();
    return false;
}


int main()
{
    int n,t=1;
    while(~scanf("%s",str)){
        if(strcmp(str,"0000000000")==0)break;
        n=str[0]-'0';
        for(int j=1,i=1;i<=9;j++,i++){
            map[(i-1)/3+1][j]=str[i]-'0';
            if(i%3==0)j=0;
        }
        /*
        for(int i=1;i<=3;i++){
            for(int j=1;j<=3;j++){
                printf("%d ",map[i][j]);
            }
            printf("
");
        }*/
        if(Get_H()==0){
            printf("%d. 0
",t++);
            continue;
        }
        for(max_deep=1;max_deep<=n;max_deep++){
            if(IDA_star(0))break;
        }
        if(max_deep>n){
            printf("%d. -1
",t++);
        }else 
            printf("%d. %d
",t++,max_deep);
    }
    return 0;
}