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Using randomize partition to avoid the basically ordered sequences

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CN-GuoZiyang
2019-07-06 20:54:55 +08:00
parent 63cf199e02
commit 7cd8552502
1 changed files with 18 additions and 3 deletions
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21
Sorts/QuickSort.java
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@ -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 @@ class QuickSort implements SortAlgorithm {
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 @@ class QuickSort implements SortAlgorithm {
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);