Merge pull request #128 from iamsunil25/quick-sort

"quick sort in java"

Author: SarthakKeshari

Sorting/quickSort.java

@@ -0,0 +1,55 @@
+//Q. how to implement quicksort in java? 
+
+
+
+class QuickSort {
+    //main method
+    public static void main(String args[]) {
+        int arr[] = { 101, 37, 68, 29, 11, 5 }; //takingthe input array 
+        System.out.println("before sorting array");
+        for (int element : arr) {
+            System.out.print(element + " "); // input = 101, 37, 68, 29, 11, 5
+        }
+        System.out.println();
+        int n = arr.length; // 6
+        QuickSort ob = new QuickSort();
+        ob.sort(arr, 0, n - 1); // here we call the sort method for sorting the array 
+
+        System.out.println("after sorting array");
+        printArray(arr); // after performing sort method now we are going to print the sorted array
+    }
+
+    // Partition Method
+    int partition(int arr[], int lowIndex, int highIndex) {
+        int pivot = arr[highIndex];
+        int i = (lowIndex - 1);
+        for (int j = lowIndex; j < highIndex; j++) {
+            if (arr[j] <= pivot) {
+                i++;
+                int temp = arr[i];
+                arr[i] = arr[j];
+                arr[j] = temp;
+            }
+        }
+        int temp = arr[i + 1];
+        arr[i + 1] = arr[highIndex];
+        arr[highIndex] = temp;
+        return i + 1;
+    }
+// method to sort array
+    void sort(int arr[], int lowIndex, int highIndex) {
+        if (lowIndex < highIndex) {
+            int pi = partition(arr, lowIndex, highIndex);
+            sort(arr, lowIndex, pi - 1); //left array of pivot
+            sort(arr, pi + 1, highIndex); //right array of pivot
+        }
+    }
+// method to print array
+    static void printArray(int arr[]) {
+        int n = arr.length;
+
+        for (int i = 0; i < n; ++i)
+            System.out.print(arr[i] + " "); //  output = 5 11 29 37 68 101 
+        System.out.println();
+    }
+}