如题，发了三个贴都没人答，跪求各位大佬大神了！！！

#include<iostream>
#include<string>
#include<queue>
#include<map>
using namespace std;
typedef long long ll;
map<ll,ll> cnt;
map<string,bool> buc;
ll head=0,tail=1;
string aim="123804765";
string str;
ll nextp(ll pos,ll id){
    switch(id){
        case 1:
            if(pos-3>0)return pos-3;
            break;
        case 2:
            if(pos+3<8)return pos+3;
            break;
        case 3:
            if(pos%3!=0)return pos-1;
            break;
        case 4:
            if(pos%3!=2)return pos+1;
            //break;
    }
    return -1;
}
void bfs(string str){
    if(str==aim){cout<<0;return;}
    queue<string> q;
    q.push(str);
    bool flag=false;
    while(!q.empty() and !flag){
        string now=q.front();q.pop();
        ll pos=now.find('0');
        for(ll i=1;i<=4;i++){
            ll ds=nextp(pos,i);
            if(ds==-1)continue;
            swap(now[pos],now[ds]);
            if(!buc[now]){
                if(now==aim){cout<<cnt[head]+1;flag=true;break;}
                cnt[tail++]=cnt[head]+1;
                q.push(now);
                buc[now]=1;
            }
            swap(now[pos],now[ds]);
        }
        head+=1;
    }
}
int main(){
    cin>>str;
    bfs(str);
    return 0;
}```