Merge pull request #147 from 24apurv/quicksort-java

Qucksort for java

Java/Quicksort.java

@@ -0,0 +1,64 @@
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class Quicksort {
+
+    /**
+     * Java method to partition array by placing elements lower than pivot to left
+     * of pivot and those higher than pivot to the right
+     * 
+     * @param int[] arr : array to be sorted
+     * @param int   low : starting index
+     * @param int   high : ending index
+     * @return index of pivot
+     */
+    public static int partition(int[] arr, int low, int high) {
+        int pivot = arr[high];
+        int i = low - 1;
+        for (int j = low; j < high; j++) {
+            if (arr[j] < pivot) {
+                i++;
+                int temp = arr[i];
+                arr[i] = arr[j];
+                arr[j] = temp;
+            }
+        }
+        arr[high] = arr[i + 1];
+        arr[i + 1] = pivot;
+        return i + 1;
+    }
+
+    /**
+     * Java method to sort array using quicksort
+     * 
+     * @param int[] arr : array to be sorted
+     * @param int   low : starting index
+     * @param int   high : ending index
+     */
+    public static void quicksort(int[] arr, int low, int high) {
+        if (low < high) {
+            int pi = partition(arr, low, high);
+            quicksort(arr, low, pi - 1);
+            quicksort(arr, pi + 1, high);
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        int n;
+        System.out.println("Enter the number of array elements: ");
+        n = sc.nextInt();
+
+        int arr[] = new int[n];
+        System.out.println("Enter the array elements: ");
+        for (int i = 0; i < n; i++)
+            arr[i] = sc.nextInt();
+
+        System.out.println("Original array : " + Arrays.toString(arr));
+        quicksort(arr, 0, arr.length - 1);
+        System.out.println("Sorted array : " + Arrays.toString(arr));
+
+        sc.close();
+    }
+}