[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=,f=;char chr=getchar();
     while(!isdigit(chr)){if(chr=='-') f=-;chr=getchar();}
     while(isdigit(chr)){ans=(ans<<)+(ans<<)+chr-;chr=getchar();}
     return ans*f;
 }int a[][],x,y,ff;char chr;
 const int S[][]={{,,,},{,,,},{,,,},{,,,}},dx[]={,,-,},dy[]={,,,-};
 inline bool check(){
     for(int i=;i<=;i++)
         for(int j=;j<=;j++)
             if(S[i][j]!=a[i][j]) return ;
     return ;
 }inline bool test(int x,int y){int ans=;
     for(int i=;i<=;i++)
         for(int j=;j<=;j++)
             if(S[i][j]!=a[i][j])
                 if(++ans+x>y) return ;
     return ;
 }void dfs(int stp,int x,int y,int depth,int lst){
     if(depth==stp){if(check()) ff=;return;}
     if(ff) return;
     for(int i=;i<;i++){
         int fx=x+dx[i],fy=y+dy[i];
         if(fx<||fy<||fx>||fy>||lst+i==) continue;
         swap(a[x][y],a[fx][fy]);
         if(test(stp,depth)&&!ff)    dfs(stp+,fx,fy,depth,i);
         swap(a[x][y],a[fx][fy]);
     }
 }
 int main(){
     for(int i=;i<=;i++)
         for(int j=;j<=;j++){cin>>chr;if(chr=='') x=i,y=j;a[i][j]=chr-;}
     if(check()){puts("");return ;}
     int i=;
     while(i++){dfs(,x,y,i,-);if(ff){cout<<i;return ;}}
     return ;
 }