hacktoberfest2020/mergeSort.cpp at master · anXcode/hacktoberfest2020 · GitHub

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#include<iostream>
using namespace std;

void merge(int arr[], int l, int mid, int r)
{
    int n1 = mid - l + 1;
    int n2 = r - mid;

    int left[n1], right[n2];

    for(int i = 0; i < n1; i++)
        left[i] = arr[l + i];
    for(int j = 0; j < n2; j++)
        right[j] = arr[mid + j + 1];

    int i = 0;
    int j = 0;

    int k = l;

    while (i < n1 && j < n2)
    {
        if (left[i] <= right[j])
        {
            arr[k] = left[i];
            i++;
        }
        else
        {
            arr[k] = right[j];
            j++;
        }
        k++;
    }

    while (i < n1)
    {
        arr[k] = left[i];
        i++;
        k++;
    }

    while (j < n2)
    {
        arr[k] = right[j];
        j++;
        k++;
    }
}

void mergeSort(int arr[], int l, int r)
{
    if (l < r){
        int mid = l + (r - l) / 2;

        mergeSort(arr, l, mid);
        mergeSort(arr, mid + 1, r);
        merge(arr, l, mid, r);
    }
}

void printArray(int arr[], int n)
{
    for(int i = 0; i < n; i++)
        cout << arr[i] << " ";
}

int main()
{
    int n;
    cout <<"Enter the number of elements: ";
    cin >> n;

    int *arr = new int[n];

    for(int i = 0; i < n; i++)
    cin >> arr[i];

    cout << "Given array is \n";
    printArray(arr, n);

    mergeSort(arr, 0, n - 1);

    cout << "\nSorted array is \n";
    printArray(arr, n);
    return 0;
}