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QuickSort.java
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77 lines (71 loc) · 2.38 KB
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package com.thealgorithms.sorts;
/**
* @author Varun Upadhyay (https://github.com/varunu28)
* @author Podshivalov Nikita (https://github.com/nikitap492)
* @see SortAlgorithm
*/
class QuickSort implements SortAlgorithm {
/**
* This method implements the Generic Quick Sort
*
* @param array The array to be sorted Sorts the array in increasing order
*/
@Override
public <T extends Comparable<T>> T[] sort(T[] array) {
doSort(array, 0, array.length - 1);
return array;
}
/**
* The sorting process
*
* @param left The first index of an array
* @param right The last index of an array
* @param array The array to be sorted
*/
private static <T extends Comparable<T>> void doSort(T[] array, final int left, final int right) {
if (left < right) {
final int pivot = randomPartition(array, left, right);
doSort(array, left, pivot - 1);
doSort(array, pivot, right);
}
}
/**
* Randomize 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, final int left, final int right) {
final int randomIndex = left + (int) (Math.random() * (right - left + 1));
SortUtils.swap(array, randomIndex, right);
return partition(array, left, right);
}
/**
* This method finds the partition index for an array
*
* @param array The array to be sorted
* @param left The first index of an array
* @param right The last index of an array Finds the partition index of an
* array
*/
private static <T extends Comparable<T>> int partition(T[] array, int left, int right) {
final int mid = (left + right) >>> 1;
final T pivot = array[mid];
while (left <= right) {
while (SortUtils.less(array[left], pivot)) {
++left;
}
while (SortUtils.less(pivot, array[right])) {
--right;
}
if (left <= right) {
SortUtils.swap(array, left, right);
++left;
--right;
}
}
return left;
}
}