PHP / Math - Getting grid values

Question

So this might be quite bizarre, but... Imagine a grid of 10x10, each numbered left to right, top to down, starting at 1 and ending in 100.

I want to input a grid number ($plot) and get each grid number that surrounds it.

I started by making an array:

$plot = 45;
$arr = array(
    $plot-11, $plot-10, $plot-9, 
    $plot-1, $plot, $plot+1, 
    $plot+9, $plot+10, $plot+11
    );

This works fine.

Except if I add a plot near the edge of the grid (like $plot = 50) it would give me results at the start of the next row. Eg:

Any clever ways to solve this?

Answer 1

您可以过滤数组并仅保留距离为1或0的单元格：

$plot = 50;
$arr = array(
    $plot-11, $plot-10, $plot-9, 
    $plot-1, $plot, $plot+1, 
    $plot+9, $plot+10, $plot+11
    );

$plotX = ($plot - 1) % 10 + 1;
$plotY = ceil($plot / 10);

$arr = array_filter($arr, function($item) use($plotX, $plotY){
    return 1 >= abs($plotX - (($item - 1) % 10 + 1))
        && 1 >= abs($plotY - ceil($item / 10));
});

var_export($arr);

结果：

array (
  0 => 39,
  1 => 40,
  3 => 49,
  4 => 50,
  6 => 59,
  7 => 60,
)