C: Merge Sort

merge.c

void merge(int* a, int n);
void mergeSort(int* a, int n);

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

#define NUM_ELEMENTS_IN(t) (sizeof(t)/sizeof(*t))

int main(int argc, char const *argv[])
{
	int a[] = {3,4,5,1,-1,-2,99,6};
	int i;
	mergeSort(a,NUM_ELEMENTS_IN(a));
	
	for (i = 0; i < NUM_ELEMENTS_IN(a); ++i)
	{
		printf("%d ",a[i]);
	}
	return 0;
}

void mergeSort(int* a, int n){

	if( n <= 1 ){
		return;
	}

	mergeSort(a, n/2 );
	mergeSort(a + n/2, n - n/2);
	merge(a, n );
}


//merge n/2 from beginning with
//n - n/2 elements from n/2+1 element
//which are sorted in increased order themselves
void merge(int* a, int n){
	int i,k = 0,m = 0;

	int* temp = (int*)malloc(sizeof(int) * n);

	for (i = 0; (i < n) && (k < n/2) && (m < (n-n/2)) ; ++i)
	{

		if( a[k] < a[n/2+m]){

			temp[i] = a[k];
			k++;
		}else{
			temp[i] = a[n/2+m];
			m++;
			
		}
	}


	if( k < n/2 ){
		for( ;k < n/2;k++ ){
			temp[i++] = a[k];
		}
	}else if( m < (n-n/2)){
		for(; m < (n-n/2); m++){
			temp[i++] = a[n/2+m];
		}
	}

	memcpy(a,temp,sizeof(int) * n);
	free(temp);
}