How to check the 4 vertical and horizontal elements in a matrix based on the current position?

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1

Let’s assume I have a matrix this way:

$matrix = [[0, 1, 1, 0],
           [1, 1, 1, 0],
           [1, 0, 0, 0]];

Imagine that you are making a loop and capturing the position of this matrix as the example below, being y the lines with my arrays and x the positions of each line (I do not know if it is correct the way to build it):

<?php

 $data = getHierarchyMatrix(['x'=>2,'y'=>1], $matrix);

 echo '<pre>';
 print_r($data);
 function getHierarchyMatrix($currentXY, $matrix) {

    $currentX = $currentXY['x'];
    $currentY = $currentXY['y'];

    foreach ($matrix as $currentLine => $arrayLine) {

           if ($currentLine >= $currentY) {
              $previousY = ($currentLine-1);
              $nextY = ($currentLine+1);
              if (isset($matrix[$previousY])) {
                 $previousValueY = $matrix[$previousY];
              }
              if (isset($matrix[$currentLine+1])) {
                 $nextValueY = $matrix[$nextY];
              }

              foreach ($arrayLine as $current => $value) {
                  if ($current == $currentX) {
                      $currentValue = $value;
                      $previousX = ($current - 1);
                      if (isset($matrix[$current][$previousX])) {
                         $previousValueX = $matrix[$current][$previousX];
                      }
                      $nextX  = ($current + 1);
                      if (isset($matrix[$current][$nextX])) {
                         $nextValueX = $matrix[$current][$nextX];
                      }
                  }
              }
          }
      }

    return [
             'atual'    => $currentValue,
             'esquerda' => $previousValueX,
             'direita'  => $nextValueX,
             'em cima'  => $previousValueY,
             'em baixo' => $nextValueY
           ];
 }

The problem is basically to take the x and y position and the 4 elements that surround them, I don’t know if I’m doing this directly... but I need to make the quadrant based on the current position, how could I do that? I don’t think my method is very well developed. Maybe there is some way to do this using some PHP function that I don’t know, someone could help me... Its that there are methods that could aid in this, as:

$atual = current($array); 
$proximo = next($array);  
$anterior = prev($array); 
$ultimo = end($array);

Obs: I will also need this formula for a Javascript version

php javascript array matrix
  • 1

    Can’t you take the elements using the position of the element itself as a reference? For example, suppose the element is in 1,1. The elements you seek are in 0,1, 1,0, 2,1 and 1,2.

  • Rola, I just don’t know how to do it. But in the example I’m already getting the position of the element itself.

  • @Rodrigorigotti, thanks also for the reply. Helped to reflect on everything.

2 answers

2


I imagine that will solve your problem:

function getHierarchyMatrix($currentXY, $matrix) {
    $currentX = $currentXY['x'];
    $currentY = $currentXY['y'];

    if(isset($matrix[$currentXY['y']][$currentXY['x']])){
        $atual = $matrix[$currentXY['y']][$currentXY['x']];

        $left = isset($matrix[$currentXY['y']][$currentXY['x']-1]) ? 
                $matrix[$currentXY['y']][$currentXY['x']-1] : false;
        $right = isset($matrix[$currentXY['y']][$currentXY['x']+1]) ?
                $matrix[$currentXY['y']][$currentXY['x']+1] : false;
        $top = isset($matrix[$currentXY['y']-1][$currentXY['x']]) ? 
                $matrix[$currentXY['y']-1][$currentXY['x']] : false;
        $bottom = isset($matrix[$currentXY['y']+1][$currentXY['x']]) ? 
                $matrix[$currentXY['y']+1][$currentXY['x']] : false;


        return [
            'atual'    => $atual,
            'esquerda' => $left,
            'direita'  => $right,
            'em cima'  => $top,
            'em baixo' => $bottom
            ];
    } else {
        return false;
    }

}

  • I think I traveled doing foreach, if I need to pick only one position, I didn’t need to get in a loop in the matrix. Thank you very much, it worked.

1

The first thing you should do is validate the position of the reference element, i.e.:

  • If the position of the element itself is valid;
  • If the element is between two rows and two columns.

After this validation, just take the desired elements based on the position of the reference element, to which we will name $x:

<?php

$a = $x[x-1, y]; // elemento à esquerda
$b = $x[x+1, y]; // elemento à direita
$c = $x[x, y-1]; // elemento acima
$d = $x[x, y+1]; // elemento abaixo

For Javascript, the logic is the same.

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