merge sort.cpp

#include<iostream>
using namespace std;


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


	int L[n1], R[n2];


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



	
	int i = 0; 

	
	int j = 0; 

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


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

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

	mergeSort(arr, 0, arr_size - 1);

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

// This code is contributed by Mayank Tyagi