ID Number: Q73853
5.00 5.10 6.00 6.00a 6.00ax 7.00 | 5.10 6.00 6.00a
MS-DOS | OS/2
Summary:
The Microsoft C and QuickC run-time library function qsort() is useful
for sorting data; however, it is necessary to provide qsort() a
compare function for the type of data being sorted. This sometimes
causes confusion when that type is a structure. The sample program
below illustrates how to use qsort() to sort an array of structures.
In the sample code, the animal structure contains both an integer,
which is the key to be sorted on, and an array of char that contains
the animal's name. The compare() function receives two pointers to
type struct animal and returns -1, 1, or 0 if the first element is
less than, greater than, or equal to the first element, respectively.
Sample Code
-----------
/* Compile options needed: none
*
* This example program uses the C runtime library function qsort()
* to sort an array of structures.
*/
#include <stdio.h>
#include <stdlib.h>
struct animal { int number;
char name[15];
};
struct animal array[10] = { { 1, "Anaconda" },
{ 5, "Elephant" },
{ 8, "Hummingbird" },
{ 4, "Dalmatian" },
{ 3, "Canary" },
{ 9, "Llama" },
{ 2, "Buffalo" },
{ 6, "Flatfish" },
{ 10, "Zebra" },
{ 7, "Giraffe" } };
void printarray(void);
int compare(struct animal *, struct animal *);
void main(void)
{
printf("List before sorting:\n");
printarray();
qsort((void *) &array, // beginning address of array
10, // number of elements in array
sizeof(struct animal), // size of each element
compare ); // pointer to compare function
printf("\nList after sorting:\n");
printarray();
}
int compare(struct animal *elem1, struct animal *elem2)
{
if ( elem1->number < elem2->number)
return -1;
else if (elem1->number > elem2->number)
return 1;
else
return 0;
}
void printarray(void)
{
int i;
for(i=0;i<10;i++)
printf("%d: Number %d is a %s\n",
i+1, array[i].number, array[i].name);
}
Additional reference words: 2.0 2.00 2.5 2.50 2.51 5.0 5.00 5.1 5.10
6.0 6.00 6.0a 6.00a 6.0ax 6.00ax 7.00