1 import java.util.LinkedList;
 2 import java.util.List;
 3 import java.util.Queue;
 4 
 5 public class Solution {
 6     public int[][] updateMatrix(int[][] matrix) {
 7         int m = matrix.length;
 8         int n = matrix[0].length;
 9 
10         Queue<int[]> queue = new LinkedList<>();
11         for (int i = 0; i < m; i++) {
12             for (int j = 0; j < n; j++) {
13                 if (matrix[i][j] == 0) {
14                     queue.offer(new int[] {i, j});
15                 }
16                 else {
17                     matrix[i][j]=Integer.MAX_VALUE;
18                 }
19             }
20         }
21 
22         int[][] dirs = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
23 
24         while (!queue.isEmpty()) {
25             int[] cell = queue.poll();
26             for (int[] d : dirs) {
27                 int r = cell[0] + d[0];
28                 int c = cell[1] + d[1];
29                 if (r < 0 || r >= m || c < 0 || c >= n ||
30                         matrix[r][c] <= matrix[cell[0]][cell[1]] + 1) continue;
31                 queue.add(new int[] {r, c});
32                 matrix[r][c]=matrix[cell[0]][cell[1]] + 1;
33             }
34         }
35 
36         return matrix;
37     }
38 }