Question

How to reverse an array upto a given index in PHP

Answer 1

function reverseUpToIndex(&$arr, $index) {
    if ($index > count($arr)) {
        echo "Index out of range";
        return;
    }
        
    for ($i = 0; $i < $index / 2; $i++) {
        $temp = $arr[$i];
        $arr[$i] = $arr[$index - $i - 1];
        $arr[$index - $i - 1] = $temp;            
    }
}
  
  
$arr = array(1, 4, 8, 0, 7, 3, 9, 5, 6);
           
$index = 5;
           
reverseUpToIndex($arr, $index);
    
print_r($arr);
  
    
    
    
    
/*
run:
    
Array
(
    [0] => 7
    [1] => 0
    [2] => 8
    [3] => 4
    [4] => 1
    [5] => 3
    [6] => 9
    [7] => 5
    [8] => 6
)
    
*/

 

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