1using System;
2
3class MergeSort {
4    public static void Merge(int[] arr, int l, int m, int r) {
5        int n1 = m - l + 1;
6        int n2 = r - m;
7        int[] L = new int[n1];
8        int[] R = new int[n2];
9        Array.Copy(arr, l, L, 0, n1);
10        Array.Copy(arr, m + 1, R, 0, n2);
11        int i = 0, j = 0, k = l;
12        while (i < n1 && j < n2) {
13            if (L[i] <= R[j]) {
14                arr[k++] = L[i++];
15            } else {
16                arr[k++] = R[j++];
17            }
18        }
19        while (i < n1) arr[k++] = L[i++];
20        while (j < n2) arr[k++] = R[j++];
21    }
22
23    public static void MergeSortRec(int[] arr, int l, int r) {
24        if (l < r) {
25            int m = (l + r) / 2;
26            MergeSortRec(arr, l, m);
27            MergeSortRec(arr, m + 1, r);
28            Merge(arr, l, m, r);
29        }
30    }
31
32    static void Main() {
33        int[] arr = {12, 11, 13, 5, 6, 7};
34        MergeSortRec(arr, 0, arr.Length - 1);
35        Console.WriteLine(string.Join(" ", arr));
36    }
37}
38

1using System;

class HeapSort {
    public void Heapify(int[] arr, int n, int i) {
        int largest = i;
        int l = 2 * i + 1;
        int r = 2 * i + 2;

        if (l < n && arr[l] > arr[largest])
            largest = l;

        if (r < n && arr[r] > arr[largest])
            largest = r;

        if (largest != i) {
            int swap = arr[i];
            arr[i] = arr[largest];
            arr[largest] = swap;
            Heapify(arr, n, largest);
        }
    }

    public void Sort(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);
        }
    }

    static void Main() {
        int[] arr = {12, 11, 13, 5, 6, 7};
        HeapSort hs = new HeapSort();
        hs.Sort(arr);
        Console.WriteLine(string.Join(" ", arr));
    }
}