Adding bucketsort

Author: Osama Sayed

algorithms/sorting/bucketsort.php

@@ -0,0 +1,84 @@
+<?php
+
+/**
+ * Description: Bucket sort is a sorting algorithm that works by partitioning an array into a number of buckets.
+ * Each bucket is then sorted separately by applying another sorting algorithm on it. Here I chose
+ * to apply insertion sort algorithm.
+ *
+ * Complexity: worst is O(n * n), average O(n+k)
+ * where k is the number of buckets
+ */
+
+$inputArray = [5, 2, 6, 6, 1, 1, 3, 4, 12, 15, 23, 11, 8];
+bucketSort($inputArray);
+print_r($inputArray);
+
+/**
+ * Function to bucketSort an array of elements.
+ *
+ * @param array $inputArray the elements to be sorted.
+ */
+function bucketSort(&$inputArray)
+{
+    $elementsCount = count($inputArray);
+    $maximumNumber =$inputArray[0];
+    $minimumNumber = $inputArray[0];
+    $buckets = [];
+
+    // get the maximum and minimum elements in the input array
+    for ($i = 1; $i < $elementsCount; $i++) {
+        if ($inputArray[$i] < $minimumNumber) {
+            $minimumNumber = $inputArray[$i];
+        }
+        if ($inputArray[$i] > $maximumNumber) {
+            $maximumNumber = $inputArray[$i];
+        }
+    }
+
+    // create buckets of length $maximumNumber - $minimumNumber +1 and each bucket is an empty array for now
+    for ($bucketIndex = 0; $bucketIndex < ($maximumNumber - $minimumNumber +1); $bucketIndex++) {
+        $buckets[$bucketIndex] = [];
+    }
+
+    // add each element in the input array to the array in the [$elementvalue - $minimumNumber] bucket
+    for ($i = 0; $i < $elementsCount; $i++) {
+        $buckets[$inputArray[$i] - $minimumNumber][] = $inputArray[$i];
+    }
+
+    // now we go through each bucket and sort its elements using insertionSort
+    foreach ($buckets as $bucket) {
+        $count = count($bucket);
+        if ($count && $count > 1) {
+            insertionSort($bucket, count($bucket));
+        }
+    }
+
+    // we now put the elements back to the original array
+    $inputArray = [];
+    foreach ($buckets as $bucket) {
+        foreach ($bucket as $bucketElement) {
+            $inputArray[] = $bucketElement;
+        }
+    }
+}
+
+/**
+ * Function to apply an insertion sort on an array.
+ *
+ * @param array $array          the array to be sorted
+ * @param int   $elementsNumber the amount of elements in the array
+ */
+function insertionSort(&$array, $elementsNumber)
+{
+    // Iterate from the second element till the last one in the array.
+    for ($currentElementIndex = 1; $currentElementIndex < $elementsNumber; $currentElementIndex++) {
+        $value = $array[$currentElementIndex];
+        $holeIndex = $currentElementIndex;
+        // going backwards through the elements of the sorted array
+        while ($holeIndex > 0 && $array[$holeIndex - 1] > $value) {
+            $array[$holeIndex] = $array[$holeIndex - 1]; // shift the larger number towards the right.
+            $holeIndex--;
+        }
+        $array[$holeIndex] = $value;
+    }
+}