leetcode——1391.检查网格中是否存在有效路径

import java.util.LinkedList;
import java.util.Queue;

class Solution {
    public boolean hasValidPath(int[][] grid) {
        int[][] visited = new int[grid.length][grid[0].length];  //创建新的数组，用于存放该位置是否已经被访问过
        Queue<int[]> queue = new LinkedList<>();     //创建链表，用于存放路径
        //方向 上下左右
        int[][] vectors = new int[][]{{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
        queue.offer(new int[]{0, 0});    //插入原点坐标
        visited[0][0] = 1;//对[0][0]位置进行标记
        Queue<int[]> queue1 = new LinkedList<>();
        while (!queue.isEmpty() || !queue1.isEmpty()) {
            if(!queue.isEmpty()) {
                int[] poll = queue.poll();  //返回队头
                if (poll[0] == grid.length - 1 && poll[1] == grid[0].length - 1)
                    return true;
                int way = 1;
                for (int[] vector : vectors) {
                    int a = poll[0] + vector[0];
                    int b = poll[1] + vector[1];
                    if (a >= 0 && a < grid.length && b >= 0 && b < grid[0].length && visited[a][b] == 0) {
                        int before = grid[poll[0]][poll[1]];
                        int after = grid[a][b];
                        if (isOk(before, after, way)) {
                            if(way!=4){
                                queue1.add(poll);
                            }
                            queue.offer(new int[]{a, b});
                            visited[a][b] = 1;
                            break;
                        }
                    }
                    way++;
                }
            }else if(!queue1.isEmpty()){
                int[] poll = queue1.poll();  //返回队头
                if (poll[0] == grid.length - 1 && poll[1] == grid[0].length - 1)
                    return true;
                int way = 1;
                for (int[] vector : vectors) {
                    int a = poll[0] + vector[0];
                    int b = poll[1] + vector[1];
                    if (a >= 0 && a < grid.length && b >= 0 && b < grid[0].length && visited[a][b] == 0) {
                        int before = grid[poll[0]][poll[1]];
                        int after = grid[a][b];
                        if (isOk(before, after, way)) {
                            queue1.offer(new int[]{a, b});
                            visited[a][b] = 1;
                            break;
                        }
                    }
                    way++;
                }
            }
        }
        return false;
    }

    private boolean isOk(int a, int b, int way) {
        // way 代表 1， 2， 3， 4
        // 分别代表 上 下 左 右
        if (way == 1) {
            if ((a == 2 || a == 5 || a == 6) && (b == 2 || b == 3 || b == 4))
                return true;
        } else if (way == 2) {
            if ((a == 2 || a == 3 || a == 4) && (b == 2 || b == 5 || b == 6))
                return true;
        } else if (way == 3) {
            if ((a == 1 || a == 3 || a == 5) && (b == 1 || b == 4 || b == 6))
                return true;
        } else if (way == 4) {
            if ((a == 1 || a == 4 || a == 6) && ((b == 1 || b == 3 || b == 5)))
                return true;
        }
        return false;
    }


    public static void main(String[] args) {
        Solution s = new Solution();
        int[][] grid = {{4,1,3},{6,1,2}};
        boolean b = s.hasValidPath(grid);
        System.out.println(b);
    }
}

 

可费了我好大劲呢，我这速度，怕是会死在路上。

效率呀效率，得提高呀。

 ——2020.6.17