Sorting Algorithms Examples

SortingAlgorithms.cs

namespace Sorting;

internal class SortingAlgorithms
{
    public static int[] BubbleSort(int[] arr)
    {
        int n = arr.Length;
        for (int i = 0; i < n - 1; i++)
        {
            for (int j = 0; j < n - i - 1; j++)
            {
                if (arr[j] > arr[j + 1])
                {
                    int temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                }
            }
        }

        return arr;
    }

    public static int[] SelectionSort(int[] arr)
    {
        int n = arr.Length;
        for (int i = 0; i < n - 1; i++)
        {
            int minIdx = i;
            for (int j = i + 1; j < n; j++)
            {
                if (arr[j] < arr[minIdx])
                {
                    minIdx = j;
                }
            }
            int temp = arr[minIdx];
            arr[minIdx] = arr[i];
            arr[i] = temp;
        }

        return arr;
    }

    public static int[] 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);
        }

        return arr;
    }

    public static int[] InsertionSort(int[] arr)
    {
        int n = arr.Length;
        for (int i = 1; i < n; ++i)
        {
            int key = arr[i];
            int j = i - 1;
            while (j >= 0 && arr[j] > key)
            {
                arr[j + 1] = arr[j];
                j = j - 1;
            }
            arr[j + 1] = key;
        }

        return arr;
    }

    public static int[] HeapSort(int[] arr)
    {
        int n = arr.Length;
        for (int i = n / 2 - 1; i >= 0; i--)
            Heapify(arr, n, i);
        for (int i = n - 1; i >= 0; i--)
        {
            int temp = arr[0];
            arr[0] = arr[i];
            arr[i] = temp;
            Heapify(arr, i, 0);
        }

        return arr;
    }

    public static int[] MergeSort(int[] arr, int left, int right)
    {
        if (left < right)
        {
            int mid = (left + right) / 2;
            MergeSort(arr, left, mid);
            MergeSort(arr, mid + 1, right);
            Merge(arr, left, mid, right);
        }

        return arr;
    }


    #region Private Methods

    private 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;
            }
        }
        int temp1 = arr[i + 1];
        arr[i + 1] = arr[high];
        arr[high] = temp1;
        return i + 1;
    }

    private static void Heapify(int[] arr, int n, int i)
    {
        int largest = i;
        int left = 2 * i + 1;
        int right = 2 * i + 2;
        if (left < n && arr[left] > arr[largest])
            largest = left;
        if (right < n && arr[right] > arr[largest])
            largest = right;
        if (largest != i)
        {
            int swap = arr[i];
            arr[i] = arr[largest];
            arr[largest] = swap;
            Heapify(arr, n, largest);
        }
    }

    private static void Merge(int[] arr, int left, int mid, int right)
    {
        int n1 = mid - left + 1;
        int n2 = right - mid;
        int[] L = new int[n1];
        int[] R = new int[n2];
        for (int x = 0; x < n1; ++x)
            L[x] = arr[left + x];
        for (int y = 0; y < n2; ++y)
            R[y] = arr[mid + 1 + y];
        int k = left;
        int i = 0, j = 0;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                j++;
            }
            k++;
        }
        while (i < n1)
        {
            arr[k] = L[i];
            i++;
            k++;
        }
        while (j < n2)
        {
            arr[k] = R[j];
            j++;
            k++;
        }
    }

    #endregion
}

SortingConsole.cs

using Sorting;

int[] willBeSorted = { 5, 3, 8, 4, 1, 2, 7, 6 };

var bubbleSorted = SortingAlgorithms.BubbleSort(willBeSorted);
var selectionSorted = SortingAlgorithms.SelectionSort(willBeSorted);
var quickSorted = SortingAlgorithms.QuickSort(willBeSorted, 0, 7);
var insertionSorted = SortingAlgorithms.InsertionSort(willBeSorted);
var heapSorted = SortingAlgorithms.HeapSort(willBeSorted);
var mergeSorted = SortingAlgorithms.MergeSort(willBeSorted, 0, 7);

foreach (var item in mergeSorted)
{
    Console.Write(item + " ");
}

Console.ReadLine();