-
Notifications
You must be signed in to change notification settings - Fork 150
/
QuickSort.kt
67 lines (63 loc) · 2.81 KB
/
QuickSort.kt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
/*
* Copyright (c) 2017 Kotlin Algorithm Club
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package io.uuddlrlrba.ktalgs.sorts
/**
* Developed by Tony Hoare in 1959, with his work published in 1961, Quicksort is an efficient sort algorithm using
* divide and conquer approach. Quicksort first divides a large array into two smaller sub-arrays: the low elements
* and the high elements. Quicksort can then recursively sort the sub-arrays. The steps are:
* 1) Pick an element, called a pivot, from the array.
* 2) Partitioning: reorder the array so that all elements with values less than the pivot come before the pivot,
* while all elements with values greater than the pivot come after it (equal values can go either way).
* After this partitioning, the pivot is in its final position. This is called the partition operation.
* 3) Recursively apply the above steps to the sub-array of elements with smaller values and separately to
* the sub-array of elements with greater values.
*/
@ComparisonSort
@UnstableSort
class QuickSort: AbstractSortStrategy() {
override fun <T : Comparable<T>> perform(arr: Array<T>) {
sort(arr, 0, arr.size - 1)
}
private fun <T : Comparable<T>> sort(arr: Array<T>, lo: Int, hi: Int) {
if (hi <= lo) return
val j = partition(arr, lo, hi)
sort(arr, lo, j - 1)
sort(arr, j + 1, hi)
}
private fun <T : Comparable<T>> partition(arr: Array<T>, lo: Int, hi: Int): Int {
var i = lo
var j = hi + 1
val v = arr[lo]
while (true) {
while (arr[++i] < v) {
if (i == hi) break
}
while (v < arr[--j]) {
if (j == lo) break
}
if (j <= i) break
arr.exch(j, i)
}
arr.exch(j, lo)
return j
}
}