Solution to "Algorithm Fridays (14-05-2021)" problem

algo_fridays_solution2.php

<?php
function shuffleClass($input_array, $num_of_stud){
	if (is_array($input_array) && count($input_array)>2 && is_integer($num_of_stud) && abs($num_of_stud) <= count($input_array)):
		
		// number is negative
		if ($num_of_stud < 0):
			for($i=0; $i<abs($num_of_stud); $i++){
				$array1[] = $input_array[$i];
			}
			$array2 = array_diff($input_array, $array1);
			return array_merge($array2, $array1);

		// number is positive
		elseif ($num_of_stud > 0):
			for($i=count($input_array)-$num_of_stud; $i<count($input_array); $i++){
				$array1[] = $input_array[$i];
			}
			$array2 = array_diff($input_array, $array1);
			return array_merge($array1, $array2);

		else:
			return $input_array;
		endif;

	else:
		return 'FALSE';
	endif;
}
?>

Hello @codelikesuraj, thank you for participating in Week 6 of #AlgorithmFridays.

This is a decent attempt at coming up with a solution for Apex College. Your solution works for most test cases and you demonstrated good knowledge of PHP in-built functions.

However, one test case your solution didn't pass is:

• When num_of_stud has a value greater than the size of the input_array list. For such cases, your solution returns FALSE because of your check on line 26. For example, shuffleClass([2, 3], 3); // yours would return FALSE instead of [3, 2]. The expectation is that when the value of num_of_stud is greater than the size of input_array, you should think of it as shuffling the entire pupils list for as many times as is possible until num_of_stud becomes less than the size of input_array. In mathematical terms, that would be num_of_stud = num_of_stud % input_array.length.

I understand that your solution was made with a lot of assumptions of how certain things should be implemented but I think it's always best to check in with your interviewer before making assumptions. I wrote about that in this article, you might find it helpful.

Please let me know your thoughts.