跳蚱蜢(Jumping Grasshoppers) 题解

思路分析

按题目要求使用对应数据结构与算法模拟/递推求解，注意数据范围边界与时间复杂度。

参考代码

#include <iostream>
#include <string>
#include <queue>
#include <unordered_map>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    string start = "012345678";
    string target = "087654321";
    unordered_map<string, int> dist;
    queue<string> q;
    dist[start] = 0;
    q.push(start);
    int d[4] = {-2, -1, 1, 2};
    while (!q.empty()) {
        string u = q.front();
        q.pop();
        int step = dist[u];
        if (u == target) {
            cout << step << "\n";
            return 0;
        }
        int pos = 0;
        while (pos < 9 && u[pos] != '0') ++pos;
        for (int k = 0; k < 4; ++k) {
            int npos = (pos + d[k] + 9) % 9;
            string v = u;
            swap(v[pos], v[npos]);
            if (dist.find(v) == dist.end()) {
                dist[v] = step + 1;
                q.push(v);
            }
        }
    }
    return 0;
}