MergeSort.c

#include <stdio.h>
#include <stdlib.h>

void printArray(int A[], int size)
{
	int i;
	for (i = 0; i < size; i++)
		printf("%d ", A[i]);
	printf("\n");
}

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

	/* create temp arrays */
	int L[n1], R[n2];

	/* Copy data to temp arrays L[] and R[] */
	for (i = 0; i < n1; i++)
		L[i] = arr[l + i];
	for (j = 0; j < n2; j++)
		R[j] = arr[m + 1 + j];

	/* Merge the temp arrays back into arr[l..r]*/
	i = 0; // Initial index of first subarray
	j = 0; // Initial index of second subarray
	k = l; // Initial index of merged subarray
	while (i < n1 && j < n2) {
		if (L[i] <= R[j]) {
			arr[k] = L[i];
			i++;
		}
		else {
			arr[k] = R[j];
			j++;
		}
		k++;
	}

	/* Copy the remaining elements of L[], if there
	are any */
	while (i < n1) {
		arr[k] = L[i];
		i++;
		k++;
	}

	/* Copy the remaining elements of R[], if there
	are any */
	while (j < n2) {
		arr[k] = R[j];
		j++;
		k++;
	}
	printf("LeftArray:\n");
	printArray(L, n1);
	printf("RightArray:\n");
	printArray(R, n2);
	printf("\n");
}

/* l is for left index and r is right index of the
sub-array of arr to be sorted */
void mergeSort(int arr[], int l, int r)
{
	if (l < r) {
		int m = (l + r) / 2;

		// Sort first and second halves
		mergeSort(arr, l, m);
		mergeSort(arr, m + 1, r);

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

void main()
{
	int n;
    printf("Enter size of array:\n"); //Input of size of array
    scanf("%d", &n);
    int arr[n];
    printf("Enter elements of the array:\n"); //Input of elements of array
    for(int i=0; i<n; i++){
        scanf("%d", &arr[i]);
    }

	mergeSort(arr, 0, n - 1);

	printf("\nSorted array is \n");
	printArray(arr, n);
}