Create Quick Sort

Author: akshayavb99

Course 2 - Data Structures in JAVA/Lecture 5 - Recursion II/Quick Sort

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+/*
+Sort an array A using Quick Sort. Change in the input array itself. So no need to return or print anything.
+
+Input format :
+Line 1 : Integer n i.e. Array size
+Line 2 : Array elements (separated by space)
+
+Output format :
+Array elements in increasing order (separated by space)
+
+Constraints :
+1 <= n <= 10^3
+
+Sample Input 1 :
+6 
+2 6 8 5 4 3
+Sample Output 1 :
+2 3 4 5 6 8
+
+Sample Input 2 :
+5
+1 5 2 7 3
+Sample Output 2 :
+1 2 3 5 7 
+*/
+
+
+public class Solution {
+	
+	public static void quickSort(int[] input) {
+		/* Your class should be named Solution
+		 * Don't write main().
+		 * Don't read input, it is passed as function argument.
+		 * No need to print or return the output.
+		 * Taking input and printing output is handled automatically.
+		 */
+        
+        quickSort(input,0,input.length-1);	
+	}
+    
+    public static void quickSort(int[] input, int si, int ei)
+    {
+        if (si>=ei)
+        {
+            return;
+        }
+        int pivotIndex=partition(input,si,ei);
+        quickSort(input, si, pivotIndex-1);
+        quickSort(input,pivotIndex+1,ei);
+    }
+    
+    public static int partition(int[] a, int si, int ei)
+    {
+        int pivotElement=a[si];
+        int smallerEleCount=0;
+        for(int i=si+1;i<=ei;i++)
+        {
+            if (a[i]<pivotElement)
+            {
+                smallerEleCount++;
+            }
+        }
+        
+        int temp=a[si+smallerEleCount];
+        a[si+smallerEleCount]=pivotElement;
+        a[si]=temp;
+        
+        int i=si;
+        int j=ei;
+        while(i<j)
+        {
+            if (a[i]<pivotElement)
+            {
+                i++;
+            }
+            else if (a[j]>=pivotElement)
+            {
+                j--;
+            }
+            else
+            {
+                temp=a[i];
+                a[i]=a[j];
+                a[j]=temp;
+                i++;
+                j--;
+            }
+        }
+        
+        return si+smallerEleCount;
+    }
+	
+}