/*------------------- bubble7.c ------------------*/
/* Program bubble_7.c from PTRTUT10.HTM              6/10/97 */
#include <stdio.h>
#include <string.h>
#define MAX_BUF 256
long arr[10] = { 3,6,1,2,3,8,4,1,7,2};
char arr2[5][20] = { "Mickey Mouse",
                      "Donald Duck",
                      "Minnie Mouse",
                      "Goofy",
                      "Ted Jensen" };
void bubble(void *p, int width, int N,
            int(*fptr)(const void *, const void *));
int compare_string(const void *m, const void *n);
int compare_long(const void *m, const void *n);
int main(void)
{
    int i;
    puts("\nBefore Sorting:\n");
    for (i = 0; i < 10; i++)               /* show the long ints */
    {
        printf("%ld ",arr[i]);
    }
    puts("\n");
    for (i = 0; i < 5; i++)                  /* show the strings */
    {
        printf("%s\n", arr2[i]);
    }
    bubble(arr, 4, 10, compare_long);           /* sort the longs */
    bubble(arr2, 20, 5, compare_string);     /* sort the strings */
    puts("\n\nAfter Sorting:\n");
    for (i = 0; i < 10; i++)             /* show the sorted longs */
    {
        printf("%d ",arr[i]);
    }
    puts("\n");
    for (i = 0; i < 5; i++)            /* show the sorted strings */
    {
        printf("%s\n", arr2[i]);
    }
    return 0;
}
void bubble(void *p, int width, int N,
            int(*fptr)(const void *, const void *))
{
    int i, j, k;
    unsigned char buf[MAX_BUF];
    unsigned char *bp = p;
    for (i = N-1; i >= 0; i--)
    {
        for (j = 1; j <= i; j++)
        {
            k = fptr((void *)(bp + width*(j-1)), (void *)(bp +
j*width));
             if (k > 0)
             {
                 memcpy(buf, bp + width*(j-1), width);
                 memcpy(bp + width*(j-1), bp + j*width , width);
                 memcpy(bp + j*width, buf, width);
             }
        }
    }
}
int compare_string(const void *m, const void *n)
{
    char *m1 = (char *)m;
    char *n1 = (char *)n;
    return (strcmp(m1,n1));
}
int compare_long(const void *m, const void *n)
{
    long *m1, *n1;
    m1 = (long *)m;
    n1 = (long *)n;
    return (*m1 > *n1);
}
/*----------------- end of bubble7.c -----------------*/

References for Chapter 10:
   1. "Algorithms in C"
      Robert Sedgewick
      Addison-Wesley
      ISBN 0-201-51425-7

EPILOG
I have written the preceding material to provide an introduction to pointers for newcomers to C. In C, the more one understands about pointers the greater flexibility one has in the writing of code. The above expands on my first effort at this which was entitled ptr_help.txt and found in an early version of Bob Stout' collection of C code SNIPPETS.
The content in this version has been updated from that in PTRTUTOT.ZIP included in SNIP9510.ZIP.
I am always ready to accept constructive criticism on this material, or review requests for the addition of other relevant material. Therefore, if you have questions, comments, criticisms, etc. concerning that which has been presented, I would greatly appreciate your contacting me via email me at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

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