Merge Sort.cpp

// ---- AI Programming ------
//Implementation of Merge Sort using C++
// Join our underground coding movement
// @freecodecs (c) May, 2019

#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[n1], R[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 = l+(r-l)/2;
 
        mergeSort(arr, l, m);
        mergeSort(arr, m+1, r);
 
        merge(arr, l, m, r);
    }
}
 

void display(int arr[], int size)
{
    int i;
    for (i=1; i < size; i++)
    cout<<arr[i]<<", ";
}
 

int main()
{
     int size;
    cout<<"\nEnter the size of elements : ";

    cin>>size;

    int arr[size];
    
    cout<<"\nBy using space enter the unsorted elements : ";

    for (int i = 0; i < size; ++i)
    {
        cin>>arr[i];
    }

    mergeSort(arr, 0, size);
 
    cout<<"\nSorted elements are : ";
    display(arr, size);
    return 0;
}