week 4 542. 01 Matrix Using DFS

public class Solution {
    public int[][] updateMatrix(int[][] matrix) {
        if(matrix.length==0) return matrix;
        for(int i = 0; i<matrix.length; i++)
            for(int j = 0; j<matrix[0].length; j++)
                if(matrix[i][j]==1&&!hasNeiberZero(i, j,matrix)) 
                    matrix[i][j] = matrix.length+matrix[0].length+1;
        
        for(int i = 0; i<matrix.length; i++)
            for(int j = 0; j<matrix[0].length; j++)
                if(matrix[i][j]==1)
                    dfs(matrix, i, j, -1);
        return matrix;
    }
    private void dfs(int[][] matrix, int x, int y, int val){
        if(x<0||y<0||y>=matrix[0].length||x>=matrix.length||matrix[x][y]<=val)
            return;
        
        if(val>0) matrix[x][y] = val;
        
        dfs(matrix, x+1, y, matrix[x][y]+1);
        dfs(matrix, x-1, y, matrix[x][y]+1);
        dfs(matrix, x, y+1, matrix[x][y]+1);
        dfs(matrix, x, y-1, matrix[x][y]+1);
        
    }
    private boolean hasNeiberZero(int x, int y, int[][] matrix){
        if(x>0&&matrix[x-1][y]==0) 
        return true;
        if(x<matrix.length-1&&matrix[x+1][y]==0) 
        return true;
        if(y>0&&matrix[x][y-1]==0) 
        return true;
        if(y<matrix[0].length-1&&matrix[x][y+1]==0) 
        return true;
        
        return false;
    }
}