sort8.c

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

typedef int T;

/**
 * [Sorting network](http://en.wikipedia.org/wiki/Sorting_network)
 */
void sort8(T ar[], int n) {
	static char cmplist2[][2] = {{0, 1}, };
	static char cmplist3[][2] = {{0, 1}, {1, 2}, {0, 1} };
	static char cmplist4[][2] = {{0, 1}, {2, 3}, {0, 2}, {1, 3}, {1, 2}, };
	static char cmplist5[][2] = {{0, 1}, {2, 3}, {0, 2}, {1, 3}, {1, 2}, {3, 4}, {2, 3}, {1, 2}, {0, 1}};
	static char cmplist6[][2] = {{0, 1}, {1, 2}, {0, 1}, {3, 4}, {4, 5}, {3, 4}, {0, 3}, {2, 5}, {1, 2}, {3, 4}, {1, 3}, {2, 4}, {2, 3}};
	static char cmplist7[][2] = {{0, 1}, {2, 3}, {0, 2}, {1, 3}, {4, 5}, {5, 6}, {4, 5}, {0, 4}, {3, 6}, {1, 2}, {2, 3}, {1, 2}, {4, 5}, {1, 4}, {3, 5}, {2, 3}, {3, 4}, {2, 3}};
	static char cmplist8[][2] = {{0, 1}, {2, 3}, {0, 2}, {1, 3}, {1, 2}, {4, 5}, {6, 7}, {4, 6}, {5, 7}, {5, 6}, {0, 4}, {2, 6}, {2, 4}, {1, 5}, {3, 7}, {3, 5}, {1, 2}, {3, 4}, {5, 6}, };
	static char lengths[] = {-1, 0, 1, 3, 5, 9, 13, 18, 19};
	static char (*lists[])[2] = {NULL, NULL, cmplist2, cmplist3, cmplist4, cmplist5, cmplist6, cmplist7, cmplist8};
	assert(n >= 0 && n <= 8);
	if (n > 1) {
		char (*list)[2] = lists[n];
		int len = lengths[n];
		int i;
		for (i = 0; i < len; ++i) {
			int a = list[i][0];
			int b = list[i][1];
			if (ar[a] > ar[b]) {
				T tmp = ar[a];
				ar[a] = ar[b];
				ar[b] = tmp;
			}
		}
	}
}

int main(int argc, char const *argv[])
{
	int ar[] = {2, 4, 3, 5, 6, 1, 7};
	sort8(ar, 7);
	int i;
	for (i = 0; i < 7; ++i) {
		printf("%d ", ar[i]);
	}
	putchar('\n');
	return 0;
}