Using randomize partition to avoid the basically ordered sequences

Author: CN-GuoZiyang

Sorts/QuickSort.java

@@ -1,6 +1,6 @@
 package Sorts;
 
-import static Sorts.SortUtils.*;
+import static sorts.SortUtils.*;
 
 /**
  * @author Varun Upadhyay (https://github.com/varunu28)
@@ -33,12 +33,27 @@ public <T extends Comparable<T>> T[] sort(T[] array) {
 
  private static <T extends Comparable<T>> void doSort(T[] array, int left, int right) {
  if (left < right) {
- int pivot = partition(array, left, right);
+ int pivot = randomPartition(array, left, right);
  doSort(array, left, pivot - 1);
  doSort(array, pivot, right);
  }
  }
 
+ /**
+ * Ramdomize the array to avoid the basically ordered sequences
+ * 
+ * @param array The array to be sorted
+ * @param left The first index of an array
+ * @param right The last index of an array
+ * @return the partition index of the array
+ */
+
+ private static <T extends Comparable<T>> int randomPartition(T[] array, int left, int right) {
+ int randomIndex = left + (int)(Math.random()*(right - left + 1));
+ swap(array, randomIndex, right);
+ return partition(array, left, right);
+ }
+
  /**
  * This method finds the partition index for an array
  *
@@ -75,7 +90,7 @@ public static void main(String[] args) {
  Integer[] array = {3, 4, 1, 32, 0, 1, 5, 12, 2, 5, 7, 8, 9, 2, 44, 111, 5};
 
  QuickSort quickSort = new QuickSort();
- // quickSort.sort(array);
+ quickSort.sort(array);
 
  //Output => 0 1 1 2 2 3 4 5 5 5 7 8 9 12 32 44 111
  print(array);