This function takes in two set of arrays, merges them and sort them using the quick sort algorithm. It returns a new array of the merged arrays in ascending order. It has a worst case time complexity of O(nlog(n)) and space complexity of 0(log(n))

SortAndMergeArrayOfStudentAges.php

<?php
function SortAndMergeArrayOfStudentAges($firstArray, $secondArray)
{
   if (gettype($firstArray) != 'array' && gettype($secondArray) != 'array') {
        return [];
    }
    if (gettype($firstArray) == 'array' && gettype($secondArray) != 'array') {
        return quickSort($firstArray);
    }

    if (gettype($firstArray) != 'array' && gettype($secondArray) == 'array') {
        return quickSort($secondArray);
    }
    return quickSort(array_merge($firstArray, $secondArray));
}


function quickSort($array)
{
    quickSortHelper($array, 0, count($array) - 1);
    return $array;
}

function quickSortHelper(&$array, $startIndex, $endIndex)
{  
    if ($startIndex >= $endIndex) {
        return;
    }
    $pivotIndex = $startIndex;
    $leftIndex = $startIndex + 1;
    $rightIndex = $endIndex;
    while ($rightIndex >= $leftIndex) {
        if ($array[$leftIndex] > $array[$pivotIndex] && $array[$rightIndex] < $array[$pivotIndex]) {
            swap($array, $leftIndex, $rightIndex);
        }
        if ($array[$leftIndex] <= $array[$pivotIndex]) {
            $leftIndex += 1;
        }
        if ($array[$rightIndex] >= $array[$pivotIndex]) {
            $rightIndex -= 1;
        }
    }
    swap($array, $pivotIndex, $rightIndex);
    $leftSubArrayIsSmaller = $rightIndex - (1 - $startIndex) < $endIndex - ($rightIndex + 1);
    if ($leftSubArrayIsSmaller) {
        quickSortHelper($array, $startIndex, $rightIndex - 1);
        quickSortHelper($array, $rightIndex + 1, $endIndex);
    } else {
        quickSortHelper($array, $rightIndex + 1, $endIndex);
        quickSortHelper($array, $startIndex, $rightIndex - 1);
    }
}
function swap(&$array, $a, $b)
{
    list($array[$a], $array[$b]) = array($array[$b], $array[$a]);
}
$firstArray = [13,15,19];
$secondArray = [11, 13, 18];
// print_r(mergeStudentAges($firstArray, $secondArray));
print_r(SortAndMergeArrayOfStudentAges($firstArray, $secondArray));

Hello @harmlessprince, thank you for participating in Week 5 of #AlgorithmFridays.

Your solution passes most of the test cases but except the one case where one of the input arrays is empty. Ideally, if one of the classes say classA is empty, your function should return classB.

SortAndMergeArrayOfStudentAges([], [3, 4, 5]); // should return [3, 4, 5] but yours returns []

What do you think?

Boss, you are right. 😂

Their is always one thing.....

I have updated the solution to accommodate that now.