intial revision

Author: ankurjuneja

Sorting/QuickSort.java

@@ -0,0 +1,54 @@
+import java.util.Arrays;
+
+public class QuickSort {
+
+    private int partition(int [] array, int low, int high)
+    {
+        int largest = array[high];
+        int i = low - 1 ; // i to keep track of smaller element
+
+        for (int j = low; j < high; j++)
+        {
+            if (array[j] <= largest)
+            {
+                i++;
+                //exchange array[i] and array[j]
+                int temp = array[i];
+                array[i] = array[j];
+                array[j] = temp ;
+            }
+        }
+
+        //exchange last smaller element with pivot
+        int temp = array[i+1];
+        array[i+1] = array[high];
+        array[high] = temp;
+
+        return i+1;
+    }
+    public void quickSort(int[] array, int low, int high)
+    {
+        if (low < high)
+        {
+            int pivot = partition(array,low,high); //pivot is the partitioning index
+
+            //recursive sort two sub arrays around pivot
+            quickSort(array,low, pivot-1);
+            quickSort(array,pivot+1,high);
+
+        }
+
+    }
+
+    public void printSortedArray(int[] array) {
+        Arrays.stream(array)
+                .forEach(num-> System.out.print(" "+num));
+    }
+
+    public static void main(String[] args) {
+        int[] arr = {16,8,7,3,1,9,4};
+        QuickSort qs = new QuickSort();
+        qs.quickSort(arr,0,arr.length-1);
+        qs.printSortedArray(arr);
+    }
+}