gaspersic/freeCodeCamp
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

feat(guide): added java implementation to quicksort (#36005)

Browse Source 
* feat: added java implementation to quicksort

* fix: edited heading in quicksort
This commit is contained in:
Ahmed Khaled
2019-07-19 23:13:50 +02:00
committed by Quincy Larson
parent 07d9862c0e
commit 830def0604
1 changed files with 88 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
guide/english/algorithms/sorting-algorithms/quick-sort/index.md
View File

@ -185,6 +185,46 @@ function [pInd, unsorted] = partition(unsorted, low, high)
end
```
### Implementation in Java
```java
public class Quicksort {
static void quickSort(int[] array, int p, int r) {
if (p < r) {
int q = partition(array, p, r);
quickSort(array, p, q - 1);
quickSort(array, q + 1, r);
}
}
static int partition(int[] array, int p, int r) {
// using the last element as the pivot
int pivot = array[r];
int i = p - 1;
for (int j = p; j <= r - 1; j++) {
if (array[j] <= pivot) {
i++;
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
int temp = array[i + 1];
array[i + 1] = array[r];
array[r] = temp;
return i + 1;
}
public static void main(String[] args) {
int [] array = {2,8,7,1,3,5,6,4};
quickSort(array, 0, 7);
for (int i : array)
System.out.print(i + " ");
}
}
```
The space complexity of quick sort is `O(n)`. This is an improvement over other divide and conquer sorting algorithms, which take `O(nlong(n))` space. Quick sort achieves this by changing the order of elements within the given array. Compare this with the <a href='https://guide.freecodecamp.org/algorithms/sorting-algorithms/merge-sort' target='_blank' rel='nofollow'>merge sort</a> algorithm which creates 2 arrays, each length `n/2`, in each function call.
@ -209,4 +249,3 @@ The space complexity of quick sort is O(n). This is an improvement over other di
- <a href='https://www.youtube.com/watch?v=SLauY6PpjW4' target='_blank' rel='nofollow'>Youtube: Gayle Laakmann McDowell (author of Cracking The Coding Interview) explains the basics of quicksort and show some implementations</a>
- <a href='https://www.youtube.com/watch?v=COk73cpQbFQ' target='_blank' rel='nofollow'>Quick Sort - MyCodeSchool</a>