如何交换多维数组中的最大和最小数字？

Question

I'm writing a program that swaps largest and smallest number in multidimensional array. Largest number should be on the place where is the smallest, and smallest where is the largest, and the idea is to use pure logic, without any php function that could help me out.

Please check my code and help me about this problem.

For instance:

$array = [
  [45, 456, 321, 344, 567],
  [100, 434, 173, 400, 789],
  [191, 211, 457, 809, 900],
  [431, 323, 432, 805, 906],
  [708, 232, 897, 101, 696]
];

New order should be:

$array = [
  [906, 456, 321, 344, 567],
  [100, 434, 173, 400, 789],
  [191, 211, 457, 809, 900],
  [431, 323, 432, 805, 45],
  [708, 232, 897, 101, 696]
]

I've tried with adding and changing code with this piece of code, but it doesn't give me right results...

$min_index = $max_index = 0;
foreach($array as $k => $v){
    if($v < $array[$min_index]){
        $min_index = $k;
    }
    if($v > $array[$max_index]){
        $max_index = $k;
    }
}
$min = $array[$min_index];
$array[$min_index] = $array[$max_index];
$array[$max_index] = $min;

$array = [
  [45, 456, 321, 344, 567],
  [100, 434, 173, 400, 789],
  [191, 211, 457, 809, 900],
  [431, 323, 432, 805, 906],
  [708, 232, 897, 101, 696]
];

$intRows = 4;
$intCols = 4;

$intMaxRow = $intMinRow = $intMaxCol = $intMinCol = 0;

$minIndex = $maxIndex = 1;

for($row = 0; $row < $intRows; $row++)
{
  for($col = 0; $col < $intCols; $col++)
  {
    if($array[$row][$col] > $maxIndex)
    {
      $maxIndex = $array[$row][$col];
      $intMaxRow = $row;
      $intMaxCol = $col;
    }
    if($array[$row][$col] < $minIndex)
    {
      $minIndex = $array[$row][$col];
      $intMinRow = $row;
      $intMinCol = $col;
    }
  }
}

$arrNxm[$intMinRow][$intMinCol] = $minIndex;
$arrNxm[$intMaxRow][$intMaxCol] = $maxIndex;

echo "<pre>";
var_dump($arrNxm);
echo "</pre>";

Answer 1

You've got some logical issues in your code which is causing it to not work. You are going along the right lines though.

Issue 1

You have set the number of rows and columns incorrectly. There are not 4, there are 5 of each:

$intRows = 5;
$intCols = 5;

Issue 2

The next issue is with:

$minIndex = $maxIndex = 1;

If $minIndex is 1 , then nothing in your array can be lower than it, so it's never going to be updated from 1. This should be something like:

$minIndex = 100000; // This is an arbitrary choice to fix the issue
$maxIndex = 1;

Issue 3

Next, you use $arrNxm in your code. There is no $arrNxm , it should be $array .

Issue 4

Finally, this is wrong because you are putting the minimum value back into the minimum position in the array:

$arrNxm[$intMinRow][$intMinCol] = $minIndex;
$arrNxm[$intMaxRow][$intMaxCol] = $maxIndex;

You just need to swap $minIndex and $maxIndex around:

$array[$intMinRow][$intMinCol] = $maxIndex;
$array[$intMaxRow][$intMaxCol] = $minIndex;

Full code

The fully working code is:

$array = [
  [45, 456, 321, 344, 567],
  [100, 434, 173, 400, 789],
  [191, 211, 457, 809, 900],
  [431, 323, 432, 805, 906],
  [708, 232, 897, 101, 696]
];

$intRows = 5;
$intCols = 5;

$intMaxRow = $intMinRow = $intMaxCol = $intMinCol = 0;

$minIndex = 100000;
$maxIndex = 1;

for($row = 0; $row < $intRows; $row++)
{
  for($col = 0; $col < $intCols; $col++)
  {
    if($array[$row][$col] > $maxIndex)
    {
      $maxIndex = $array[$row][$col];
      $intMaxRow = $row;
      $intMaxCol = $col;
    }
    if($array[$row][$col] < $minIndex)
    {
      $minIndex = $array[$row][$col];
      $intMinRow = $row;
      $intMinCol = $col;
    }
  }
}

$array[$intMinRow][$intMinCol] = $maxIndex;
$array[$intMaxRow][$intMaxCol] = $minIndex;

echo "<pre>";
var_dump($array);
echo "</pre>";

This outputs:

array(5) {
  [0]=>
  array(5) {
    [0]=>
    int(906)
    [1]=>
    int(456)
    [2]=>
    int(321)
    [3]=>
    int(344)
    [4]=>
    int(567)
  }
  [1]=>
  array(5) {
    [0]=>
    int(100)
    [1]=>
    int(434)
    [2]=>
    int(173)
    [3]=>
    int(400)
    [4]=>
    int(789)
  }
  [2]=>
  array(5) {
    [0]=>
    int(191)
    [1]=>
    int(211)
    [2]=>
    int(457)
    [3]=>
    int(809)
    [4]=>
    int(900)
  }
  [3]=>
  array(5) {
    [0]=>
    int(431)
    [1]=>
    int(323)
    [2]=>
    int(432)
    [3]=>
    int(805)
    [4]=>
    int(45)
  }
  [4]=>
  array(5) {
    [0]=>
    int(708)
    [1]=>
    int(232)
    [2]=>
    int(897)
    [3]=>
    int(101)
    [4]=>
    int(696)
  }
}

Whereby 45 and 906 are swapped in position as you wanted.