sort_four_numbers_without_arrays_and_loops_v2.c

/*

    sort_four_numbers_without_arrays_and_loops_v2.c

A nice way to do small, fixed-size sorts is using a sorting network:
https://en.wikipedia.org/wiki/Sorting_network

int tmp;
if (a > b) { tmp = a; a = b; b = tmp; }
if (c > d) { tmp = c; c = d; d = tmp; }
if (a > c) { tmp = a; a = c; c = tmp; }
if (b > d) { tmp = b; b = d; d = tmp; }
if (b > c) { tmp = b; b = c; c = tmp; }

Each line codes a comparison and swap between two elements.
You can use this page to generate optimal sorting networks for small numbers of inputs.
http://pages.ripco.net/~jgamble/nw.html
To sort in reverse order, just flip the > signs to < signs.


    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

#include <stdio.h>

// To sort in decrease order, just flip the > signs to < signs.
void sort_four_numbers_without_arrays_and_loops( int *a, int *b, int *c, int *d )
{
    int tmp;

    if (*a > *b) { tmp = *a; *a = *b; *b = tmp; printf("\n %d  %d  %d  %d \n", *a, *b, *c, *d ); }
    if (*c > *d) { tmp = *c; *c = *d; *d = tmp; printf("\n %d  %d  %d  %d \n", *a, *b, *c, *d ); }
    if (*a > *c) { tmp = *a; *a = *c; *c = tmp; printf("\n %d  %d  %d  %d \n", *a, *b, *c, *d ); }
    if (*b > *d) { tmp = *b; *b = *d; *d = tmp; printf("\n %d  %d  %d  %d \n", *a, *b, *c, *d ); }
    if (*b > *c) { tmp = *b; *b = *c; *c = tmp; printf("\n %d  %d  %d  %d \n", *a, *b, *c, *d ); }
}

int main(void)
{
//  int a=2, b=1, c=4, d=3;
//  int a=4, b=2, c=1, d=3;
    int a=4, b=3, c=2, d=1;

    printf("\n a  b  c  d \n %d  %d  %d  %d \n", a, b, c, d );

    sort_four_numbers_without_arrays_and_loops( &a, &b, &c, &d );

    printf("\n a  b  c  d \n %d  %d  %d  %d \n", a, b, c, d );


    return 0;

} // main()