P1379 八数码难题

https://www.luogu.org/problemnew/show/P1379 

 

#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<iostream>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<ctime>
#include<map>
#include<stack>
#include<string>
#include<ctime>
using namespace std;

#define sfi(i) scanf("%d",&i)
#define pri(i) printf("%d\n",i)
#define sff(i) scanf("%lf",&i)
#define ll long long
#define mem(x,y) memset(x,y,sizeof(x))
#define INF 0x3f3f3f3f
#define eps 1e-14
#define PI acos(-1)
#define lowbit(x) ((x)&(-x))
#define zero(x) (((x)>0?(x):-(x))<eps)
#define fl() printf("flag\n")
#define MOD(x) ((x%mod)+mod)%mod
#define FASTIO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
ll gcd(ll a,ll b){while(b^=a^=b^=a%=b);return a;}
const int maxn=1e6+9;
const int mod=1e8+7;

inline ll read()
{
    ll f=1,x=0;
    char ss=getchar();
    while(ss<'0'||ss>'9'){if(ss=='-')f=-1;ss=getchar();}
    while(ss>='0'&&ss<='9'){x=x*10+ss-'0';ss=getchar();}
    return f*x;
}

int gol[10]={5,1,2,3,6,9,8,7,4};
int dis[11][11];
int now[10];
int mp[11][11],tmp[11][11];
int dx[5]={0,0,1,-1};
int dy[5]={1,-1,0,0};
bool f=0;
int h()
{
    int sum=0;
    for(int i=1;i<9;i++)
    {
        sum+=dis[now[i]][gol[i]];
    }
    return sum;
}
bool ch()
{
    for(int i=0;i<9;i++) if(now[i]!=gol[i]) return 0;
    return 1;
}
void mdis()
{
    for(int i=1;i<=9;i++)
    {
        for(int j=1;j<=9;j++)
        {
            int jj=j%3?j%3:3;
            int ii=i%3?i%3:3;
            dis[i][j]=abs((i-1)/3-(j-1)/3)+abs(jj-ii);
        }
    }
}
void dfs(int g,int x,int y,int st)
{
    if(f) return ;
    if(g+h()>st) return ;
    if(ch())
    {
        f=1;
        return ;
    }

    for(int i=0;i<4;i++)
    {
        int tx=x+dx[i];
        int ty=y+dy[i];
        if(tx>=1&&ty>=1&&tx<=3&&ty<=3)
        {
            swap(tmp[x][y],tmp[tx][ty]);
            swap(now[tmp[x][y]],now[tmp[tx][ty]]);
            dfs(g+1,tx,ty,st);
            swap(tmp[x][y],tmp[tx][ty]);
            swap(now[tmp[x][y]],now[tmp[tx][ty]]);
        }
    }

}
int main()
{
    //FASTIO;
    //#define endl '\n'
    mdis();
    string s;
    int cnt=0;
    cin>>s;
    int sx=0,sy=0;
    for(int i=1;i<=3;i++)
    {
        for(int j=1;j<=3;j++)
        {
            int k=s[cnt++]-'0';
            mp[i][j]=k;
            if(k==0) sx=i,sy=j;
            now[k]=(i-1)*3+j;
        }
    }
    int st=0;
    while(1)
    {
        memcpy(tmp,mp,sizeof(mp));
        dfs(0,sx,sy,st);
        if(f)
        {
            cout<<st<<endl;
            break;
        }
        st++;
    }
    return 0;
}