Transposing Arrays in PHP: A Matrix Manipulation Exercise | CodeSignal Learn

Transposing Arrays in PHP: A Matrix Manipulation Exercise | CodeSignal Learn

Introduction

Hello there! Are you ready to enhance your PHP programming skills with an exciting exercise? In this unit, we are diving into the world of matrices . More specifically, we'll be transposing a given matrix. Let's embark on this matrix manipulation adventure without delay!

Task Statement

To begin, let's elaborate on the task at hand. You are required to write a PHP function named transformMatrix() . This function will accept a 2D array (which represents a matrix) that contains integers as inputs. Your responsibility is to return another 2D array, which is the transposed version of the given matrix. Remember, when we mention "transposing a matrix," we are referring to the process of switching its rows and columns. In other words, all the rows of the original matrix should convert into columns in the transposed matrix, and vice versa. For instance, if the original matrix (input 2D array) is: $matrix = [[1, 2, 3], [4, 5, 6]]; Then the transposed matrix (output 2D array) will be: $transposed = [[1, 4], [2, 5], [3, 6]]; It is vital for your result to maintain the integrity of the data type that is present in the original matrix. In simpler terms, the values seen in the input matrix are integers, and they should remain integers in the output matrix as well.

Solution Building: Step 1

Solution Building: Step 2

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The initial step of building our solution involves determining the dimensions of the matrix. We need to know the number of rows and columns present in it. In PHP, the count() function can offer this information. The number of rows is simply the count of the outer array, and the number of columns matches the count of any of the inner arrays.

PHP

function transformMatrix($matrix) {
    $rows = count($matrix);
    $cols = $rows > 0 ? count($matrix[0]) : 0;
    // If rows > 0, the above line sets cols to
    // count of the first row, else sets to 0
}

The subsequent step is to create a "placeholder" for the transposed matrix that aligns with its required dimensions. This will be a new 2D array, but with the number of rows and columns swapped. Initially, this matrix can be populated with all zeros.

PHP

function transformMatrix($matrix) {
    $rows = count($matrix);
    $cols = $rows > 0 ? count($matrix[0]) : 0;
    $result = array_fill(0, $cols, array_fill(0, $rows, 0));
}

Solution Building: Step 3

It's time to get to the crux of the matter — transposing the matrix. For every element in the original matrix, we want to move it from the ith row and jth column to the jth row and ith column of the transposed matrix. A straightforward nested for-loop can effortlessly execute this swap for all elements of the matrix. PHP<?php function transformMatrix($matrix) { $rows = count($matrix); $cols = $rows > 0 ? count($matrix[0]) : 0; $result = array_fill(0, $cols, array_fill(0, $rows, 0)); for ($i = 0; $i < $rows; ++$i) { for ($j = 0; $j < $cols; ++$j) { $result[$j][$i] = $matrix[$i][$j]; } } return $result; } // Initial matrix (2D array) $matrix = [ [1, 2, 3], [4, 5, 6] ]; // Call our function on the matrix and output the result $transposed = transformMatrix($matrix); foreach ($transposed as $row) { foreach ($row as $elem) { echo $elem . " "; } echo "\n"; } This step concludes our solution!