03 Jul

C# Quick Sort Algorithm Implementation

Quicksort algorithm is a sorting algorithm developed by Tony Hoare that, on average, makes O(n log n) comparisons to sort n items.

For more information about Quick Sort Algorithm:
http://en.wikipedia.org/wiki/Quicksort

Implementation and Usage:

            int[] arr = new int[10]
            {
                1, 5, 4, 11, 20, 8, 2, 98, 90, 16
            };

            QuickSort(arr, 0, arr.Length - 1);
            Console.WriteLine("Sorted Values:");
            for (int i = 0; i < arr.Length; i++)
                Console.WriteLine(arr[i]);

            //Output:
            //Sorted Values:
            //1
            //2
            //4
            //5
            //8
            //11
            //16
            //20
            //90
            //98
        private void QuickSort(int[] arr, int start, int end)
        {
            int i;
            if (start < end)
            {
                i = Partition(arr, start, end);

                QuickSort(arr, start, i - 1);
                QuickSort(arr, i + 1, end);
            }
        }

        private int Partition(int[] arr, int start, int end)
        {
            int temp;
            int p = arr[end];
            int i = start - 1;

            for (int j = start; j <= end - 1; j++)
            {
                if (arr[j] <= p)
                {
                    i++;
                    temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
            }

            temp = arr[i + 1];
            arr[i + 1] = arr[end];
            arr[end] = temp;
            return i + 1;
        }

See Also:

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