Invert A Binary Tree in PHP (Array Implementation)

invert-binary-tree.php

<?php
// Similar, but not quite the same as LeetCode problem #226
// @see https://leetcode.com/problems/invert-binary-tree/description/

function invertTree(array $nodes): array
{
    $height = (int) floor(log(count($nodes), 2));
    $level = 1;
    while ($level <= $height) {
        $start = 2 ** $level - 1;
        $end = 2 * $start;
        while ($end > $start) {
            $temp = $nodes[$start];
            $nodes[$start] = $nodes[$end];
            $nodes[$end] = $temp;
            $end--;
            $start++;
        }
        $level++;
    }
    return $nodes;
}

var_export(invertTree([4,2,7,1,3,6,9]));