Convert1DArrayInto2DArray.php

<?php

namespace App;

/**
 * Convert 1D Array Into 2D Array
 *
 * You are given a 0-indexed 1-dimensional (1D) integer array original, and two integers, m and n. You are tasked with
 * creating a 2-dimensional (2D) array with  m rows and n columns using all the elements from original. The elements
 * from indices 0 to n - 1 (inclusive) of original should form the first row of the constructed 2D array, the elements
 * from indices n to 2 * n - 1 (inclusive) should form the second row of the constructed 2D array, and so on.
 * Return an m x n 2D array constructed according to the above procedure, or an empty 2D array if it is impossible.
 *
 * Example 1:
 * Input: original = [1,2,3,4], m = 2, n = 2
 * Output: [[1,2],[3,4]]
 * Explanation: The constructed 2D array should contain 2 rows and 2 columns.
 * The first group of n=2 elements in original, [1,2], becomes the first row in the constructed 2D array.
 * The second group of n=2 elements in original, [3,4], becomes the second row in the constructed 2D array.
 *
 * Example 2:
 * Input: original = [1,2,3], m = 1, n = 3
 * Output: [[1,2,3]]
 * Explanation: The constructed 2D array should contain 1 row and 3 columns.
 * Put all three elements in original into the first row of the constructed 2D array.
 *
 * Example 3:
 * Input: original = [1,2], m = 1, n = 1
 * Output: []
 * Explanation: There are 2 elements in original.
 * It is impossible to fit 2 elements in a 1x1 2D array, so return an empty 2D array.
 *
 * https://leetcode.com/problems/convert-1d-array-into-2d-array
 */
class Convert1DArrayInto2DArray
{
    /**
     * @param int[] $original
     * @param int $m
     * @param int $n
     * @return int[][]
     */
    public function construct2DArray(array $original, int $m, int $n): array
    {
        $arr = [];
        $lastIndex = 0;
        $row = $lastIndex;

        if (count($original) === $m * $n) {
            while ($lastIndex < count($original)) {
                $columnAmount = $n;

                while ($columnAmount > 0) {
                    $arr[$row][] = $original[$lastIndex];
                    $lastIndex++;
                    $columnAmount--;
                }

                $row++;
            }
        }

        return $arr;
    }
}