Adding radixsort

Author: Osama Sayed

algorithms/sorting/radixsort.php

@@ -0,0 +1,72 @@
+<?php
+
+/**
+ * Description: Radix sort is a sorting algorithm that is used to sort numbers by
+ * sorting them from the least significant digit to the most significant.
+ */
+
+
+$inputArray = [10, 15, 1, 60, 5, 100, 25, 50];
+radixSort($inputArray);
+var_dump($inputArray);
+
+/**
+ * Function to radix sort an array.
+ *
+ * @param array $inputArray array of elements to be sorted
+ */
+function radixSort(&$inputArray)
+{
+    $maximumElement = $inputArray[0];
+    $elementsCount = count($inputArray);
+    $buckets = [];
+    // create an array of 10 elements
+    for ($i = 0; $i < 10; $i++) {
+        $buckets[$i] = [];
+    }
+
+    // get the maximum number in the input array
+    for ($i = 1; $i < $elementsCount; $i++) {
+        if ($inputArray[$i] > $maximumElement) {
+            $maximumElement = $inputArray[$i];
+        }
+    }
+    $digitsOfMaxElement = strlen($maximumElement);
+    // adding leading zeros to all digits that are not of the same length of the largest element
+    foreach ($inputArray as $inputIndex => $inputElement) {
+        $inputArray[$inputIndex] = sprintf('%0'.$digitsOfMaxElement.'d', $inputElement);
+    }
+
+    // start from the right most digit of the input elements
+    $digitIndex = $digitsOfMaxElement -1;
+    // we need to make digitsOfMaxElement passes
+    for ($passIndex = 1; $passIndex <= $digitsOfMaxElement; $passIndex++) {
+        // go through all elements in the inputArray
+        foreach ($inputArray as $inputElement) {
+            // get the digit number $digitIndex + 1
+            $digit = $inputElement[$digitIndex];
+            // put it in the corresponding bucket
+            $buckets[$digit][] = $inputElement;
+        }
+
+        $inputArray = [];
+        // take the elements back from the buckets into the original array
+        foreach ($buckets as $bucketArray) {
+            foreach ($bucketArray as $bucketElement) {
+                $inputArray[] = $bucketElement;
+            }
+        }
+
+        // re-initialize the bucket
+        foreach ($buckets as $bucketIndex => $bucketArray) {
+            $buckets[$bucketIndex] = [];
+        }
+        $digitIndex--;
+    }
+
+    // remove the leading zero of elements by casting the elements to int
+    foreach ($inputArray as &$element) {
+        $element = (int) $element;
+    }
+}
+