MergeSort.cpp

#include <iostream>
using namespace std;

void merge(int arr[],int l,int m,int r) {
    int i, j, k;
    int n1 = m - l + 1;
    int n2 = r - m;


    int* L = new int[n1];
    int* R = new int[n2];

    for ( i = 0; i < n1; i++)
    {
        L[i] = arr[l + i];
    }
    for (j = 0; j < n2; j++)
    {
        R[j] = arr[m + 1 + j];
    }

    i = 0;
    j = 0;
    k = l;

    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 l,int r) {
    if (l<r)
    {
        int m = (r + l) / 2;
        mergeSort(arr,l,m);
        mergeSort(arr, m + 1, r);

        merge(arr,l,m,r);
    }
}

void printArray(int A[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        cout << A[i]<<" ";

    cout << endl;
    
}

int main()
{
    int arr[] = { 12, 11, 13, 5, 6, 7 };
    int arr_size = sizeof(arr) / sizeof(arr[0]);


    cout << "Given array is" << endl;
    printArray(arr, arr_size);

    mergeSort(arr, 0, arr_size - 1);

    
    cout << "Sorted array is" << endl;
    printArray(arr, arr_size);
    return 0;
}