八码数 · 哈希+BFS

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//本代码还未ac

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define between(x, a, b) (a<=x && x<=b)
const int dir[4][2] = {1, 0, 0, 1, -1, 0, 0, -1};
const int N = 1e6 + 10;
int n, m, K;
int f[15], vis[N];

struct node {
    string s="";
    int pos;//x的位置
    int step;
};

int id(string s) { //一种哈希方式 变排列
    int res = 0;
    for (int i = 0; i < 9; ++i) {
        int d = 0;
        for (int j = 0; j < i; ++j) {
            if (s[j] > s[i]) d++;
        }
        res += d * f[i];
    }
    return res;
}

int dfs(node st) {
    vis[id(st.s)] = 1;
    queue<node> q;
    q.push(st);
    while (!q.empty()) {
        auto u = q.front();
        q.pop();

        if (u.s == "123456789x") return u.step;
        if(vis[id(u.s)])continue;
        vis[id(u.s)]=1;

        int x = u.pos / 3;
        int y = u.pos % 3;
        for (int i = 0; i < 4; ++i) {
            int dx = x + dir[i][0];
            int dy = y + dir[i][1];
            if (between(dx, 0, 2) && between(dy, 0, 2)) {
                int now = dx * 3 + dy;
                swap(u.s[u.pos], u.s[now]);
                if (vis[id(u.s)]) continue;

                node v = {u.s, now, u.step + 1};
                q.push(v);
                swap(u.s[u.pos], u.s[now]);
            }
        }
    }
    return -1;
}

int main() {
    ios::sync_with_stdio(0);
    f[0] = 1; //预处理 n!
    for (int i = 1; i <= 9; ++i) {
        f[i] = f[i - 1] * i;
    }
    string s;
    node start;
    for (int i = 0; i < 9; ++i) {
        cin >> s;
        if (s == "x") start.pos = i;
        start.s += s;
    }
    cout << dfs(start) << endl;

    return 0;
}

来源：CSDN

作者：Zaller

链接：https://blog.csdn.net/Yubing792289314/article/details/104722241