From bbec0ebacf0604c8ae6b05b15ca7d08e3cbf4137 Mon Sep 17 00:00:00 2001
From: Muhammed Sabah <muhammedsabah@icloud.com>
Date: Sat, 30 Jan 2021 17:57:31 +0530
Subject: [PATCH] Added QuickSort in java (#50)

* added merge sort in java

* Added QuickSort in java
---
 sorting/README.md            |  1 +
 sorting/java/quick-sort.java | 81 ++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)
 create mode 100644 sorting/java/quick-sort.java

diff --git a/sorting/README.md b/sorting/README.md
index b7ed7f81..84457784 100644
--- a/sorting/README.md
+++ b/sorting/README.md
@@ -26,6 +26,7 @@
 2. [Insertion Sort](java/insertion-sort.java)
 3. [Selection Sort](java/selection-sort.java)
 4. [Merge Sort](java/merge-sort.java)
+5. [Quick Sort](java/quick-sort.java)
 
 ### JavaScript
 
diff --git a/sorting/java/quick-sort.java b/sorting/java/quick-sort.java
new file mode 100644
index 00000000..e61ac08b
--- /dev/null
+++ b/sorting/java/quick-sort.java
@@ -0,0 +1,81 @@
+// Java program for implement Quick Sort
+//Note: Rightmost element in the array is choosen as pivot
+class QuickSortBack
+{
+	private int[] arr;
+	public QuickSortBack()
+	{
+		arr = new int[]{222,64,545,99,12,35,1,87,33,945,77}; // Array to be sorted
+
+	}
+
+	//Function to swap two Array elements
+	public void swap(int index1 , int index2)
+	{
+		int x = arr[index1];                             //first value in temporary variable x
+		arr[index1] = arr[index2];  
+		arr[index2] = x;
+
+	}
+
+	//Function to print the Array
+	public void displayArray()
+	{
+		for (int i=0;i<arr.length;i++)
+			System.out.print(arr[i]+" ");
+		System.out.println();
+	}
+
+	// Function to partition the Array 
+	public int partitionFn(int left,int right,int pivot)
+	{
+		int leftptr = left -1;
+		int rightptr = right;
+		while (true)
+		{
+			while (arr[++leftptr]<pivot);                  //Find bigger item than pivot
+			while (rightptr>0 && arr[--rightptr]>pivot);   //Find smaller item
+
+			if (leftptr>=rightptr)                           //if index numbers cross,partition is done
+				break;
+			else
+				swap(leftptr,rightptr);                      //swap elements
+
+		}
+		swap(leftptr,right);                                 //restore pivot element
+	return leftptr;                                          //return pivot location
+	}
+
+	//Recursive quicksort function
+	public void recQuickSort(int left,int right)
+	{
+		if (right-left <= 0)                                 // already sorted if size is 1
+			return;
+		else
+		{
+			int pivot = arr[right];                          //choosing pivot as rightmost(end) element of Array
+			int partition = partitionFn(left,right,pivot);
+			recQuickSort(left,partition-1);                  //Sort left
+			recQuickSort(partition+1,right);                 //Sort right
+
+		}
+	}
+
+	//function called in main
+	public void quickSort()
+	{
+		recQuickSort(0,arr.length-1);
+	}
+}
+
+class QuickSort
+{	
+	//Driver code to test above
+	public static void main(String[] args) {
+		
+		QuickSortBack ob = new QuickSortBack();
+		ob.displayArray();                         //display array before sort
+		ob.quickSort();							   //call quickSort
+		ob.displayArray();
+	}
+}
\ No newline at end of file