JAVA

How to perform quick sort, in Java?

/*
	This is an implementation of the quick sort algorithm.

	Let n be the size of the list to sort
	Best: O(nlog2(n)) time | O(log2(n)) space
	Average: O(nlog2(n)) time | O(log2(n)) space
	Worst: O(n^2) time | O(log2(n)) space
*/
import java.util.Arrays;

public class QuickSort {
	public static void main(String[] args) {
		int[] arr = { 1, 10, 5, 3, 6 };
		quickSort(arr);
		// Below prints: [1, 3, 5, 6, 10]
		System.out.println(Arrays.toString(arr));
	}

	public static void quickSort(int[] array) {
		// Sort array recursively
		quickSortUtil(array, 0, array.length - 1);
	}

	private static void quickSortUtil(int[] array, int startIdx, int endIdx) {
		// Base case: at this point array is sorted
		if (startIdx >= endIdx) {
			return;
		}
		// Let first value be pivot
		// Sort every other number wrt to pivot
		int pivotIdx = startIdx;
		int leftIdx = startIdx + 1;
		int rightIdx = endIdx;
		// Make sure that element at leftIdx <= to one at pivotIdx
		// and element at rightIdx is >= to one at pivotIdx
		while (leftIdx <= rightIdx) {
			if (array[leftIdx] > array[pivotIdx] && array[rightIdx] < array[pivotIdx]) {
				swap(leftIdx, rightIdx, array);
			}
			if (array[leftIdx] <= array[pivotIdx]) {
				leftIdx++;
			}
			if (array[rightIdx] >= array[pivotIdx]) {
				rightIdx--;
			}
		}

		swap(pivotIdx, rightIdx, array);
		// At the end of current iteration, element at
		// pivot is in its final sorted position
		quickSortUtil(array, startIdx, rightIdx - 1);
		quickSortUtil(array, rightIdx + 1, endIdx);
	}

	private static void swap(int i, int j, int[] array) {
		int temp = array[i];
		array[i] = array[j];
		array[j] = temp;
	}
}

Quick Sort Java Implementation

// Java implementation of QuickSort
import java.io.*;
 
class GFG{
     
// A utility function to swap two elements
static void swap(int[] arr, int i, int j)
{
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}
 
/* This function takes last element as pivot, places
   the pivot element at its correct position in sorted
   array, and places all smaller (smaller than pivot)
   to left of pivot and all greater elements to right
   of pivot */
static int partition(int[] arr, int low, int high)
{
     
    // pivot
    int pivot = arr[high];
     
    // Index of smaller element and
    // indicates the right position
    // of pivot found so far
    int i = (low - 1);
 
    for(int j = low; j <= high - 1; j++)
    {
         
        // If current element is smaller
        // than the pivot
        if (arr[j] < pivot)
        {
             
            // Increment index of
            // smaller element
            i++;
            swap(arr, i, j);
        }
    }
    swap(arr, i + 1, high);
    return (i + 1);
}
 
/* The main function that implements QuickSort
          arr[] --> Array to be sorted,
          low --> Starting index,
          high --> Ending index
 */
static void quickSort(int[] arr, int low, int high)
{
    if (low < high)
    {
         
        // pi is partitioning index, arr[p]
        // is now at right place
        int pi = partition(arr, low, high);
 
        // Separately sort elements before
        // partition and after partition
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}
 
// Function to print an array
static void printArray(int[] arr, int size)
{
    for(int i = 0; i < size; i++)
        System.out.print(arr[i] + " ");
         
    System.out.println();
}
 
// Driver Code
public static void main(String[] args)
{
    int[] arr = { 10, 7, 8, 9, 1, 5 };
    int n = arr.length;
     
    quickSort(arr, 0, n - 1);
    System.out.println("Sorted array: ");
    printArray(arr, n);
}
}
 
// This code is contributed by Ayush Choudhary

quick sort function java

  static void swap(int[] arr, int i, int j) {
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
  }  
  
  static int partition(int[] arr, int low, int high) { 
    
    int pivot = arr[high]; 
    // Index of smaller element and
    // indicates the right position
    // of pivot found so far
    int i = (low - 1); 
  
    for(int j = low; j <= high - 1; j++) {
      // If current element is smaller 
      // than the pivot
      if (arr[j] < pivot) {
        // Increment index of 
        // smaller element
        i++; 
        swap(arr, i, j);
      }
    }
    swap(arr, i + 1, high);
    return (i + 1);
  }
  
  static void quickSort(int[] arr, int low, int high) {
      if (low < high) {
          // pi is partitioning index, arr[p]
          // is now at right place 
          int pi = partition(arr, low, high);

          // Separately sort elements before
          // partition and after partition
          quickSort(arr, low, pi - 1);
          quickSort(arr, pi + 1, high);
      }
  }

quick sort in java progrmmieren

package quickSort;

import java.util.Arrays;

public class Main {

    private int[] A;

    public int[] getA() {
        return A;
    }

    public void setA(int[] a) {
        A = a;
    }

    public static void main(String[] args) {
        Main a = new Main();
        int[] A = {2, 1, 9, 7, 4, 8, 10, 5, 6, 3};
        a.setA(A);
        a.quickSort(0, A.length-1);
        System.out.println(Arrays.toString(a.getA()));
    }

    public void quickSort(int l, int r){
        if(l < r){System.out.println(Arrays.toString(getA()));
            int m = partition(l, r);
            System.out.println(getA()[m]);
            quickSort(l, m-1);System.out.println(Arrays.toString(getA()));
            quickSort(m+1, r);System.out.println(Arrays.toString(getA()));

        }
    }

    public int partition(int l, int r) {
        int pivot = getA()[r];
        int i = l;
        for(int j = l; j < r; j++){
            if(getA()[j] <= pivot){
                swap(i, j);
                i++;
            }
        }
        swap(i, r);
        return i;
    }

    public void swap(int i, int r){
        int[] A = getA();
        int lel = A[i];
        A[i] = A[r];
        A[r] = lel;
        setA(A);
    }
}