mergesort.cpp

#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 a[n1];int b[n2];
    for (int i = 0; i < n1; i++)
    {a[i] = arr[l + i];}
    for (int i = 0; i < n1; i++)
    { b[i] = arr[mid + i + 1]; }
    int i = 0;int j = 0; int k = l;
    while (i < n1 && j < n2)
    {
        if (a[i] < b[j])
        {
            arr[k] = a[i];
            k++;
            i++;
        }
        else
        {
            arr[k] = b[j];
            k++;
            j++;
        }
    }
    while (i < n1)
    {
        arr[k] = a[i];
        k++;
        i++;
    }
    while (j < n2)
    {
        arr[k] = b[j];
        k++;
        j++;
    }
}
void mergesort(int arr[], int l, int r)
{
    if (l < r)
    {
        int mid = (l + r) / 2;
        mergesort(arr, l, mid);
        mergesort(arr, mid + 1, r);
        merge(arr, l, mid, r);
    }
}
int main()
{
    int n;cin>>n;
    int arr[n];
    for(int i = 0;i<n;i++)
    {cin>>arr[i];}
    mergesort(arr, 0, 4);
    for (int i = 0; i < 5; i++)
    {
        cout << arr[i] << " ";
    }
    cout << endl;
    return 0;
}