Implementing Quick Sort Algorithm

src/main/java/com/thealgorithms/divideandconquer/QuickSort.java

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+import java.util.Arrays;
+package com.thealgorithms.divideandconquer;
+
+//Java Program to Implement Quick Sort Algorithm for Sorting
+
+/*
+ * Uses Divide and Conquer Approach for Sorting
+ * Time Complexity: O(nlogn) as an average case and O(n^2) for the worst case (Sorted Array)
+ * Space Complexity: O(n)
+ *
+ * Reference:
+ * https://www.geeksforgeeks.org/quick-sort-algorithm/
+**/
+public class QuickSort
+{
+    //Function to find Partition Index
+    public static int partition(int []arr, int start, int end)
+    {
+        int pivot = arr[end];
+        int index = start-1;
+        //Dividing Array into 2 parts where left of partition index is all values less than it and right of it all values more than it
+        for(int i=start; i<=end-1;i++)
+        {
+            if(arr[i]<pivot)
+            {
+                index++;
+                swap(arr,index,j);
+            }
+        }
+        swap(arr,index+1,end)
+    }
+    //Function to swap 2 elements in an array given 2 indices
+    public static void swap(int[] arr, int index1, int index2) 
+    {
+        int temp = arr[index1];
+        arr[index1] = arr[index2];
+        arr[index2] = temp;
+    }
+    //Function to sort given array
+    public static void quicksort(int []arr, int start, int end)
+    {
+        if(start<end)
+        {
+            int partitionindex = partition(arr,start,end);
+            quicksort(arr,start,partitionindex-1);
+            quicksort(arr,partitionindex+1,end);
+        }
+    }
+}