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import java.io.*;
import java.util.*;
class {
public static void main (String[] args) {
System.out.println("Hello Java");
int[] a= {3, 2,1};
int[] b = quickSort(a);
System.out.println(Arrays.toString(b));
}
public static int[] quickSort(int[] arr) {
if (arr == null || arr.length <= 1) {
return arr;
}
sort(arr, 0, arr.length - 1);
return arr;
}
private static void sort(int[] arr, int left, int right) {
if (left >= right) {
return;
}
int pivot = partition(arr, left, right);
sort(arr, left, pivot - 1);
sort(arr, pivot + 1, right);
}
private static int partition(int[] arr, int left, int right) {
int pivotIndex = findPivot(left, right);
int pivot = arr[pivotIndex];
swap(pivotIndex, right, arr);
int leftBound = left, rightBound = right - 1;
while (leftBound <= rightBound) {
if (arr[leftBound] < pivot) {
leftBound++;
} else if (arr[rightBound] >= pivot) {
rightBound--;
} else {
swap(leftBound, rightBound, arr);
leftBound++;
rightBound--;
}
}
swap(right, leftBound, arr);
return leftBound;
}
private static void swap(int i, int j, int[] arr) {
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
private static int findPivot(int left, int right) {
Random rand = new Random();
return left + rand.nextInt(right - left + 1);
}
}
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