// C# program for implementation of QuickSort 

using System; 

​

public class GFG { 

    /* This function takes last element as pivot, 

    places the pivot element at its correct 

    position in sorted array, and places all 

    smaller (smaller than pivot) to left of 

    pivot and all greater elements to right 

    of pivot */

    static int partition(int []arr, int low, 

                                int high) 

    { 

        int pivot = arr[high]; 

        // index of smaller element 

        int i = (low - 1); 

        for (int j = low; j < high; j++) 

        { 

            // If current element is smaller 

            // than the pivot 

            if (arr[j] < pivot) 

            { 

                i++; 

​

                // swap arr[i] and arr[j] 

                int temp = arr[i]; 

                arr[i] = arr[j]; 

                arr[j] = temp; 

            } 

        } 

​

        // swap arr[i+1] and arr[high] (or pivot) 

        int temp1 = arr[i+1]; 

        arr[i+1] = arr[high]; 

        arr[high] = temp1; 

​

        return i+1; 

    } 

​

​

    /* The main function that implements QuickSort() 

    arr[] --> Array to be sorted, 

    low --> Starting index, 

    high --> Ending index */

    static void quickSort(int []arr, int low, int high) 

    { 

        if (low < high) 

        { 

            /* pi is partitioning index, arr[pi] is 

            now at right place */

            int pi = partition(arr, low, high); 

​

            // Recursively sort elements before 

            // partition and after partition 

            quickSort(arr, low, pi-1); 

            quickSort(arr, pi+1, high); 

        } 

    } 

​

    // A utility function to print array of size n 

    static void printArray(int []arr, int n) 

    { 

        for (int i = 0; i < n; ++i) 

            Console.Write(arr[i] + " "); 

        Console.WriteLine(); 

    } 

​

    // Driver program 

    public static void Main() 

    { 

        int []arr = {1, 7, 8, 9, 1, 5}; 

        int n = arr.Length; 

        quickSort(arr, 0, n-1); 

        Console.WriteLine("sorted array "); 

        printArray(arr, n); 

    } 

}