sort2.c

#include <stdio.h>

#define LEN 8
int a[LEN] = {5, 2, 4, 7, 1, 3, 2, 6};

void merge(int start, int mid, int end)
{
	int n1 = mid - start + 1;
	int n2 = end - mid;
	int left[n1], right[n2];
	int i, j, k;

	for (i = 0; i < n1; i++){
		left[i] = a[start+i];
	}
	for (j = 0; j < n2; j++){
		right[j] = a[mid+1+j];
	}

	i = j = 0;
	k = start;
	while (i < n1 && j < n2){
		if (left[i] < right[j]){
			a[k++] = left[i++];
		}else{
			a[k++] = right[j++];
		}
	}

	while (i < n1){
		a[k++] = left[i++];
	}
	while (j < n2){
		a[k++] = right[j++];
	}
}

void sort(int start, int end)
{
	int mid;
	if (start < end){
		mid = (start + end) / 2;
		printf("sort (%d-%d, %d-%d) %d %d %d "
			 "%d %d %d %d %d\n", start, mid, mid+1, end,
			 a[0], a[1], a[2], a[3], a[4], a[5],
			 a[6], a[7]);
		sort(start, mid);
		sort(mid+1, end);
		merge(start, mid, end);
		printf("merge (%d-%d, %d-%d) to %d %d %d "
			 "%d %d %d %d %d\n", start, mid, mid+1, end,
			 a[0], a[1], a[2], a[3], a[4], a[5],
			 a[6], a[7]);
	}
}

int main(int argc, char const *argv[])
{
	sort(0, LEN-1);
	return 0;
}