#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
/** Our old friend die from ex17. */
void die(const char *message)
{
 if(errno) {
MAIN
PREVIOUS
NEXT
HELP
Follow
@lzsthw
 if(errno) {
 perror(message);
 } else {
 printf("ERROR: %sn", message);
 }
 exit(1);
}
// a typedef creates a fake type, in this
// case for a function pointer
typedef int (*compare_cb)(int a, int b);
/**
 * A classic bubble sort function that uses the
 * compare_cb to do the sorting.
 */
int *bubble_sort(int *numbers, int count, compare_cb cmp)
{
 int temp = 0;
 int i = 0;
 int j = 0;
 int *target = malloc(count * sizeof(int));
 if(!target) die("Memory error.");
 memcpy(target, numbers, count * sizeof(int));
 for(i = 0; i < count; i++) {
 for(j = 0; j < count - 1; j++) {
 if(cmp(target[j], target[j+1]) > 0) {
 temp = target[j+1];
 target[j+1] = target[j];
 target[j] = temp;
 }
 }
 }
 return target;
}
int sorted_order(int a, int b)
{
 return a - b;
}
int reverse_order(int a, int b)
{
 return b - a;
}
int strange_order(int a, int b)
{
 if(a == 0 || b == 0) {
 return 0;
 } else {
 return a % b;
 }
}
/**
 * Used to test that we are sorting things correctly
 * by doing the sort and printing it out.
 */
void test_sorting(int *numbers, int count, compare_cb cmp)
{
 int i = 0;
 int *sorted = bubble_sort(numbers, count, cmp);
 if(!sorted) die("Failed to sort as requested.");
 for(i = 0; i < count; i++) {
 printf("%d ", sorted[i]);
 }
 printf("n");
 free(sorted);
}
int main(int argc, char *argv[])
{
 if(argc < 2) die("USAGE: ex18 4 3 1 5 6");
 int count = argc - 1;
 int i = 0;
 char **inputs = argv + 1;
 int *numbers = malloc(count * sizeof(int));
 if(!numbers) die("Memory error.");
 for(i = 0; i < count; i++) {
 numbers[i] = atoi(inputs[i]);
 }
 test_sorting(numbers, count, sorted_order);
 test_sorting(numbers, count, reverse_order);
 test_sorting(numbers, count, strange_order);
 free(numbers);
 return 0;
}