DSA/MergeSort.cpp at main · crazyads69/DSA · GitHub

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#include <iostream>
using namespace std;

void Merge(int arr[], int left, int mid, int right)
{
    int i, j, k;
    int n1 = mid - left + 1;
    int n2 = right - mid;
    int L[n1], R[n2];
    for (i = 0; i < n1; i++)
        L[i] = arr[left + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[mid + 1 + j];
    i = 0;
    j = 0;
    k = left;
    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++;
    }
}

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

int main()
{
    int arr[] = {5, 4, 3, 2, 1};
    int n = sizeof(arr) / sizeof(arr[0]);
    MergeSort(arr, 0, n - 1);
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
    return 0;
}