sort_four_numbers_with_names_without_arrays_and_loops_v1.c

/*

    sort_four_numbers_with_names_without_arrays_and_loops_v1.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>

struct Number_and_name
{
    int num;
    char name[10];
};

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

    if ( (*a).num > (*b).num )              // (*a).num  is same as  a->num
    {
        tmp = *a;
        *a = *b;
        *b = tmp;
        printf("\n %d  %d  %d  %d \n", (*a).num, (*b).num, (*c).num, (*d).num );
    }

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

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

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

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


int main(void)
{
    struct Number_and_name a, b, c, d;

    a.num = 4;
    sprintf( a.name, "first" );

    b.num = 3;
    sprintf( b.name, "second" );

    c.num = 2;
    sprintf( c.name, "third" );

    d.num = 1;
    sprintf( d.name, "fourth" );

    printf("\n   a \t  b \t  c \t d \n   %d \t  %d \t  %d \t %d \n %s  %s  %s  %s \n",
            a.num, b.num, c.num, d.num,
            a.name, b.name, c.name, d.name );

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

    printf("\n   a \t  b \t  c \t d \n   %d \t  %d \t  %d \t %d \n %s  %s  %s  %s \n",
            a.num, b.num, c.num, d.num,
            a.name, b.name, c.name, d.name );


    return 0;

} // main()