0542 01 Matrix

Question

My Solution:

class Solution {
    public int[][] updateMatrix(int[][] mat) {
        int row = mat.length;
        int col = mat[0].length;
        
        int[][] dirs = {
            {0, 1},
            {0,-1},
            {1, 0},
            {-1,0}
        };
        
        int[][] visited = new int[row][col];
        Queue<int[]> q = new LinkedList<>();
        
        for(int i=0; i<row; i++){
            for(int j=0; j<col; j++){
                if(mat[i][j] == 0){
                    q.offer(new int[]{i,j});
                    visited[i][j] = 1;;
                }
            }
        }
        
        int step = 1;
        while(!q.isEmpty()){
            int size = q.size();
            for(int k=0; k<size; k++){
                int[] temp = q.poll();
                for(int[] dir: dirs){
                    int x = temp[0] + dir[0];
                    int y = temp[1] + dir[1];
                    if(x >= 0 && x<row && y>=0 && y<col && visited[x][y] == 0){
                        visited[x][y] = 1;
                        mat[x][y] = step;
                        q.add(new int[]{x,y});
                    }
                }
            }
            step++;
        }
        return mat;
    }
}