01-Matrix

public class Solution {
    int m, n;
    int[][] directions = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    
    public int[][] updateMatrix(int[][] matrix) {
        m = matrix.length;
        n = matrix[0].length;
        
        int[][] result = new int[m][n];
        
        Queue<int[]> que = new LinkedList<>();
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] == 0) {
                    result[i][j] = 0;
                    que.offer(new int[] {i, j});
                }
                else {
                    result[i][j] = -1;
                }
            }
        }

        while (!que.isEmpty()) {
            int[] cell = que.poll();
            int i = cell[0];
            int j = cell[1];
            
            for (int[] dir : directions) {
                
                int new_i = i + dir[0];
                int new_j = j + dir[1];
                
                if(new_i >= 0 && new_i < m && new_j >= 0 && new_j < n && result[new_i][new_j] == -1) {
                    result[new_i][new_j] = result[i][j] + 1;
                    que.add(new int[] {new_i, new_j});
                }
            }
        }
        
        return result;
    }
}