merge_sort.c

/* C program for Merge Sort */
#include <stdio.h>
#include <stdlib.h>

void merge(int arr[], int l, int m, int r)
{
    int i , j , k  ;
    int n1 , n2 ;
    n1 = m-l+1;
    n2 = r-m ;
    int L[n1];
    int 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 printArray(int A[], int size)
{
	int i;
	for (i = 0; i < size; i++)
		printf("%d ", A[i]);
	printf("\n");
}

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

	printf("Given array is \n");
	printArray(arr, arr_size);
	mergeSort(arr, 0, arr_size - 1);

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