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普通bfs预处理 通过康拓展开进行状压 找出所有符合题意的排列

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

struct node
{
    int val;
    int id;
    char dir;
};

node que[500000];
int book[500000];
int pre[10],num[10];
int head,tail;

void init()
{
    int i;
    pre[0]=1;
    for(i=1;i<=8;i++)
    {
        pre[i]=pre[i-1]*i;
    }
    return;
}

int calI(int *ary)
{
    int i,j,res,cnt;
    res=0;
    for(i=1;i<=9;i++)
    {
        cnt=0;
        for(j=i+1;j<=9;j++)
        {
            if(ary[i]>ary[j]) cnt++;
        }
        res+=pre[9-i]*cnt;
    }
    return res;
}

void calII(int *ary,int val)
{
    int bit[20],bk[20];
    int i,j,cnt;
    for(i=1;i<=9;i++)
    {
        bit[i]=val/pre[9-i];
        val%=pre[9-i];
    }
    memset(bk,0,sizeof(bk));
    for(i=1;i<=9;i++)
    {
        cnt=0;
        for(j=1;j<=9;j++)
        {
            cnt+=(bk[j]^1);
            if(cnt>bit[i]) break;
        }
        bk[j]=1;
        ary[i]=j;
    }
    return;
}

void bfs()
{
    node cur;
    int ary[20];
    int i,p,t,val,flag;
    head=1,tail=0;
    tail++;
    que[tail].val=0;
    que[tail].id=-1;
    que[tail].dir=0;
    book[0]=1;
    while(head<=tail)
    {
        cur=que[head];
        head++;
        calII(ary,cur.val);
        for(i=1;i<=9;i++)
        {
            if(ary[i]==9)
            {
                p=i;
                break;
            }
        }
        if(p-3>=1)//up
        {
            t=ary[p-3],ary[p-3]=ary[p],ary[p]=t;
            val=calI(ary);
            if(!book[val])
            {
                tail++;
                que[tail].val=val;
                que[tail].id=head-1;
                que[tail].dir='d';
                book[val]=tail;
            }
            t=ary[p-3],ary[p-3]=ary[p],ary[p]=t;
        }
        if(p+3<=9)//down
        {
            t=ary[p+3],ary[p+3]=ary[p],ary[p]=t;
            val=calI(ary);
            if(!book[val])
            {
                tail++;
                que[tail].val=val;
                que[tail].id=head-1;
                que[tail].dir='u';
                book[val]=tail;
            }
            t=ary[p+3],ary[p+3]=ary[p],ary[p]=t;
        }
        if((p-1)/3==(p-2)/3)//left
        {
            t=ary[p-1],ary[p-1]=ary[p],ary[p]=t;
            val=calI(ary);
            if(!book[val])
            {
                tail++;
                que[tail].val=val;
                que[tail].id=head-1;
                que[tail].dir='r';
                book[val]=tail;
            }
            t=ary[p-1],ary[p-1]=ary[p],ary[p]=t;
        }
        if((p-1)/3==p/3)//right
        {
            t=ary[p+1],ary[p+1]=ary[p],ary[p]=t;
            val=calI(ary);
            if(!book[val])
            {
                tail++;
                que[tail].val=val;
                que[tail].id=head-1;
                que[tail].dir='l';
                book[val]=tail;

            }
            t=ary[p+1],ary[p+1]=ary[p],ary[p]=t;
        }
    }
    return;
}

void output(int cur)
{
    if(que[cur].id==-1) return;
    printf("%c",que[cur].dir);
    output(que[cur].id);
    return;
}

int main()
{
    int i,val;
    char ch[2];
    init();
    bfs();
    while(scanf("%s",ch)!=EOF)
    {
        if(ch[0]=='x') num[1]=9;
        else num[1]=ch[0]-'0';
        for(i=2;i<=9;i++)
        {
            scanf("%s",ch);
            if(ch[0]=='x') num[i]=9;
            else num[i]=ch[0]-'0';
        }
        val=calI(num);
        if(val==0)
        {
            printf("lr\n");
        }
        else if(!book[val])
        {
            printf("unsolvable\n");
        }
        else
        {
            output(book[val]);
            printf("\n");
        }
    }
    return 0;
}