Forked from unnisworld/simplified and readable quick sort
Created
March 17, 2019 11:10
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import java.util.Arrays; | |
public class QuickSort { | |
public static void main(String[] args) { | |
int arr[] = {11,12,13,14,15,16,17,10}; | |
sort(arr, 0, arr.length-1); | |
System.out.println("Sorted Array :"+ Arrays.toString(arr)); | |
int arr2[] = {6,5,4,3,2}; | |
sort(arr2, 0, arr2.length-1); | |
System.out.println("Sorted Array :"+ Arrays.toString(arr2)); | |
} | |
static void sort(int[] arr, int l, int r) { | |
if (l < r) | |
{ | |
int p = partition(arr, l, r); | |
sort(arr, l, p-1); | |
sort(arr, p+1, r); | |
} | |
} | |
static int partition(int arr[], int l, int r) { | |
// Take last element as pivot. | |
int pivotIndex = r; | |
int pivot = arr[pivotIndex]; | |
// This is a special variable that will keep track of the first | |
// element from the left of the array that is greater than the pivot. | |
int indexOfFirstElementGreaterThanPivot = l; | |
for(int i=l;i<r;i++) { | |
if(arr[i] <= pivot) { | |
// When you find an element smaller than pivot | |
// exchange it with first element greater than pivot. | |
swap(arr, i, indexOfFirstElementGreaterThanPivot); | |
indexOfFirstElementGreaterThanPivot ++; | |
} | |
} | |
// position pivot at the right place by swapping it with | |
// first element greater than pivot. | |
swap(arr, indexOfFirstElementGreaterThanPivot, pivotIndex); | |
int newPivotIndex = indexOfFirstElementGreaterThanPivot; | |
return newPivotIndex; | |
} | |
static void swap(int[] arr, int i, int j) { | |
int t = arr[i]; | |
arr[i] = arr[j]; | |
arr[j] = t; | |
} | |
} |
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