_1091.java

package com.fishercoder.solutions.secondthousand;

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

public class _1091 {
    public static class Solution1 {
        // you can count in the normal four directions first, then count the diagonal ones to form
        // this array
        int[] directions = new int[] {0, 1, 1, 0, -1, 1, -1, -1, 0};

        public int shortestPathBinaryMatrix(int[][] grid) {
            int m = grid.length;
            int n = grid[0].length;
            if (grid[0][0] == 1 || grid[m - 1][n - 1] == 1) {
                return -1;
            }
            int minPath = 0;
            Queue<int[]> queue = new LinkedList<>();
            queue.offer(new int[] {0, 0});
            boolean[][] visited = new boolean[m][n];
            visited[0][0] = true;
            while (!queue.isEmpty()) {
                int size = queue.size();
                for (int i = 0; i < size; i++) {
                    int[] curr = queue.poll();
                    if (curr[0] == m - 1 && curr[1] == n - 1) {
                        return minPath + 1;
                    }
                    for (int j = 0; j < directions.length - 1; j++) {
                        int newx = directions[j] + curr[0];
                        int newy = directions[j + 1] + curr[1];
                        if (newx >= 0
                                && newx < n
                                && newy >= 0
                                && newy < n
                                && !visited[newx][newy]
                                && grid[newx][newy] == 0) {
                            queue.offer(new int[] {newx, newy});
                            visited[newx][newy] = true;
                        }
                    }
                }
                minPath++;
            }
            return -1;
        }
    }
}