八数码难题

我又来写题解了~~~

我的方法：IDA*+曼哈顿

代码奉上，客官慢慢享用~

#include<bits/stdc++.h>
using namespace std;
string st,ed;
int depth;
int hfunc(string st){
int ans=0;
for (register int i=0;i<st.size();++i){
if (st[i]=='0') continue;
int j=ed.find(st[i]),r=i/3,c=i%3;
int x=j/3,y=j%3;
ans+=abs(r-x)+abs(c-y);
}
return ans;
}
const int dx[4] = {1, -1, 0, 0}, dy[4] = {0, 0, -1, 1};
bool dfs(int now,int pre){
int cnt=hfunc(st);
if(!cnt) return 1;
if(now+cnt>depth) return 0;
int pos=st.find('0'),x=pos/3,y=pos%3;
for (register int i=0;i<4;++i){
int nx=x+dx[i],ny=y+dy[i];
if(nx<0||nx>2||ny<0||ny>2||nx*3+ny==pre) continue;
swap(st[pos], st[nx*3+ny]);
if(dfs(now+1,pos))return 1;
swap(st[pos], st[nx*3+ny]);
}
return 0;
}
int main(){
freopen("eight.in","r",stdin);
freopen("eight.out","w",stdout);
cin>>st;
ed="123804765";
depth=hfunc(st);
while(depth<=27&&!dfs(0,-1))++depth;
cout<<depth<<endl;
}