链接：773. 滑动谜题

题解：https://blog.csdn.net/INGNIGHT/article/details/131350054

滑动拼图 II

class Solution {
public:
    int slidingPuzzle(vector<vector<int>>& board) {
        // 异常判断
        if (board.size() <= 0 || board[0].size() <= 0) {
            return 0;
        }
        int m = board.size();
        int n = board[0].size();
        // 将矩阵归一化为字符串
        std::string begin;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                begin += (board[i][j] + '0');
            }
        }
        // 终点
        std::string end = "123450";
        // bfs遍历队列
        std::deque<std::string> que;
        que.push_back(begin);
        // 距离起点的距离
        std::unordered_map<std::string, int> distance;
        distance[begin] = 0;
        // 一直遍历到队列为空
        while (!que.empty()) {
            auto f = que.front();
            que.pop_front();
            // 获得从当前0位置可以置换的四周位置
            for (auto& neigh : get_neighbord(m, n, f)) {
                // 如果当前位置遍历过
                if (distance.find(neigh) != distance.end()) {
                    continue;
                }
                // 放入队列
                que.push_back(neigh);
                // 更新距离
                distance[neigh] = distance[f] + 1;
            }
        }
        // 判断是否到达最终点
        return distance.find(end) == distance.end() ? -1 : distance[end];
    }
private:
    std::vector<std::string> get_neighbord(int m, int n, const std::string& node) {
        std::vector<std::string> neighboards;
        // 初始化空间
        neighboards.reserve(4);
        std::vector<std::vector<int>> direction{{0, -1}, {0, 1}, {1, 0}, {-1, 0}};
        // 获得当前空块0的位置
        int index = node.find('0');
        // 转换为所在矩阵中位置
        int row = index / n;
        int col = index % n;
        // 遍历4个方向，或者置换后的字符串
        for (int i = 0; i < direction.size(); ++i) {
            int next_row = row + direction[i][0];
            int next_col = col + direction[i][1];
            // 判断异常边界
            if (next_row < 0 || next_col < 0
                    || next_row >= m || next_col >= n) {
                continue;
            }
            // 计算下一个位置点，置换字符串
            int next_pos = next_row * n + next_col;
            std::string bak = node;
            swap(bak[index], bak[next_pos]);
            // 追加邻居，置换后的字符串
            neighboards.push_back(bak);
        }
        return neighboards;
    }
};