MergeSort.cpp

#include <iostream>
using namespace std;

void merge(int arr[], int left, int mid, int right)
{
  int n1 = mid - left + 1, n2 = right - mid;
  int L[n1], R[n2];

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

  int i = 0, j = 0, k = left;
  while (i < n1 && j < n2)
  {
    if (L[i] <= R[j])
      arr[k++] = L[i++];
    else
      arr[k++] = R[j++];
  }

  while (i < n1)
    arr[k++] = L[i++];
  while (j < n2)
    arr[k++] = R[j++];
}

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[] = {12, 11, 13, 5, 6, 7};
  int n = sizeof(arr) / sizeof(arr[0]);
  mergeSort(arr, 0, n - 1);

  cout << "Sorted array: ";
  for (int i = 0; i < n; i++)
    cout << arr[i] << " ";
}