算法.bfs八数码

#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#include<unordered_map>
using namespace std;
int dx[4] = { 1,-1,0,0 };
int dy[4] = { 0,0,-1,1 };
int bfs(string state)
{
    queue<string>q;
    unordered_map<string, int>d;
    q.push(state);
    d[state] = 0;
    while (q.size())
    {
        auto t = q.front();
 
        int dis = d[t];
        int k = t.find('x');
        int x = k / 3, y = k % 3;
 
        q.pop();
        string end = "12345678x";
        if (t == end)return d[t];
        for (int i = 0; i < 4; i++)
        {
            int a = x + dx[i], b = y + dy[i];
            if (a >= 0 && a < 3 && b >= 0 && b < 3)
            {
                swap(t[a * 3 + b], t[k]);
                if (!d.count(t))
                {
                    d[t] = dis + 1;
                    q.push(t);
                }
                swap(t[a * 3 + b], t[k]);
            }
            
        }
    }
    
    return -1;
}
 
int main()
{
    string state;
    for (int i = 0; i < 9; i++)
    {
        char s;
        cin >> s;
        state += s;
    }
    cout << bfs(state);
    return 0;
}