LQB2017A02跳蚱蜢

bfs通解，，，用了set存放状态以保证第一次找到目标答案

//
// Created by snnnow on 2020/7/29.
//

#include<bits/stdc++.h>
using namespace std;
struct node {
    string str;
    int step;
    int pos;
    node (string str,int step,int pos):str(str),pos(pos),step(step){}
};
set <string> vis;
queue <node> q;
void Insert_Inq(node temp,int i)
{
    string str = temp.str;
    swap(str[temp.pos],str[(temp.pos+i+9)%9]);
    if(vis.count(str)==0)
    {
        vis.insert(str);
        node n (str,temp.step+1,(temp.pos+i+9)%9);
        q.push(n);
    }
}
int main ()
{

    node first ("012345678",0,0);
    q.push(first);
    while (!q.empty())
    {
        node temp = q.front();
        if(temp.str=="087654321")
        {
            cout<<temp.step;
            break;
        }
        else {
            Insert_Inq(temp,1);
            Insert_Inq(temp,-1);
            Insert_Inq(temp,2);
            Insert_Inq(temp,-2);
            q.pop();
        }
    }
    return 0;
}