mergesort.c

#include <stdio.h>    
void merge(int arr[], int l, int m, int r)  
{  
    int i, j, k;  
    int n1 = m - l + 1;  
    int n2 = r - m;  
    int L[n1], 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);  
    }  
}  
int main()  
{ int i,arr_size;
	int *arr;
	printf("\nEnter size of array");
	scanf("%d",&arr_size);
	arr=malloc(arr_size*sizeof(int));
	printf("\nENter elements of the array :-");
	for(i=0;i<arr_size;i++){
		printf("\nEnter element no.%d : ",i);
		scanf("%d",arr+i);
	}  
    mergeSort(arr, 0, arr_size - 1); 
    printf("\nSorted array is \n");  
    for (i = 0; i < arr_size; i++)  
        printf("%d ", arr[i]);  
    return 0;  
}