LeetCode 1036. Escape a Large Maze

一种重新映射坐标，收缩空间的解法

原题链接：Escape a Large Maze
参考自 @qb_2008 发布于讨论区的帖子

代码：

class Solution {
    void gen_map(map<int, int>& a, int x) {
        if (x > 0) a[x-1] = 0;
        a[x] = 0;
        if (x+1 < 1000000) a[x+1] = 0;
    }
public:
    bool isEscapePossible(vector<vector<int>>& blocked, vector<int>& source, vector<int>& target) {
        map<int, int> x_map, y_map;
        for (const auto& ele: blocked) {
            gen_map(x_map, ele[0]), gen_map(y_map, ele[1]);
        }
        gen_map(x_map, source[0]), gen_map(y_map, source[1]);
        gen_map(x_map, target[0]), gen_map(y_map, target[1]);
        int x_size = 0, y_size = 0;
        for (auto& ele: x_map) ele.second = x_size++;
        for (auto& ele: y_map) ele.second = y_size++;
        vector<vector<bool>> grid(x_size, vector<bool>(y_size));
        for (const auto& ele: blocked) grid[x_map[ele[0]]][y_map[ele[1]]] = true;
        // for (int i = 0; i < x_size; ++i) {
        //     for (int j = 0; j < y_size; ++j) {
        //         if (i == x_map[source[0]] && j == y_map[source[1]])
        //             cout << 2 << " ";
        //         else if (i == x_map[target[0]] && j == y_map[target[1]])
        //             cout << 3 << " ";
        //         else
        //             cout << grid[i][j] << " ";
        //     }
        //     cout << endl;
        // }
        queue<int> que;
        que.push(x_map[source[0]] << 10 | y_map[source[1]]);
        grid[x_map[source[0]]][y_map[source[1]]] = true;
        static const int direc[][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
        while (!que.empty()) {
            int cur = que.front(); que.pop();
            int x = cur >> 10, y = cur & 0x3ff;
            if (x == x_map[target[0]] && y == y_map[target[1]]) return true;
            for (int i = 0; i < 4; ++i) {
                int nx = x + direc[i][0];
                int ny = y + direc[i][1];
                if (nx < 0 || nx >= x_size || ny < 0 || ny >= y_size) continue;
                if (!grid[nx][ny]) {
                    grid[nx][ny] = true;
                    que.push(nx << 10 | ny);
                }
            }
        }
        return false;
    }
};