[Luogu2324]八数码难题

抱歉...我可能真的做搜索上瘾了...

 

还是IDA*，自己看看就好了...

 

注意一下搜索顺序

 

#include<cstdio>
#include<queue>
#include<iostream>
#include<cstring>
using namespace std;
inline int read(){
    int ans=0,f=1;char chr=getchar();
    while(!isdigit(chr)){if(chr=='-') f=-1;chr=getchar();}
    while(isdigit(chr)){ans=(ans<<3)+(ans<<1)+chr-48;chr=getchar();}
    return ans*f;
}int a[4][4],x,y,ff;char chr;
const int S[4][4]={{0,0,0,0},{0,1,2,3},{0,8,0,4},{0,7,6,5}},dx[4]={0,1,-1,0},dy[4]={1,0,0,-1};
inline bool check(){
    for(int i=1;i<=3;i++)
        for(int j=1;j<=3;j++)
            if(S[i][j]!=a[i][j]) return 0;
    return 1;
}inline bool test(int x,int y){int ans=0;
    for(int i=1;i<=3;i++)
        for(int j=1;j<=3;j++)
            if(S[i][j]!=a[i][j])
                if(++ans+x>y) return 0;
    return 1;
}void dfs(int stp,int x,int y,int depth,int lst){
    if(depth==stp){if(check()) ff=1;return;}
    if(ff) return;
    for(int i=0;i<4;i++){
        int fx=x+dx[i],fy=y+dy[i];
        if(fx<1||fy<1||fx>3||fy>3||lst+i==3) continue;
        swap(a[x][y],a[fx][fy]);
        if(test(stp,depth)&&!ff)    dfs(stp+1,fx,fy,depth,i);
        swap(a[x][y],a[fx][fy]);
    }
}
int main(){
    for(int i=1;i<=3;i++)
        for(int j=1;j<=3;j++){cin>>chr;if(chr=='0') x=i,y=j;a[i][j]=chr-48;}
    if(check()){puts("0");return 0;}
    int i=1;
    while(i++){dfs(0,x,y,i,-1);if(ff){cout<<i;return 0;}}
    return 0;
}