使用qsort进行排序

使用man qsort查看原型

void qsort(void *base, size_t nmemb, size_t size,
                  int(*compar)(const void *, const void *));

 

 

 

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/time.h>

#define SIZE(__arr)	(sizeof(__arr[0]))
#define NMEMB(__arr) 	(sizeof(__arr) / SIZE(__arr))

struct bucket {
	char a;
	int b;
	int c;
};

unsigned int
seed_get(void)
{
	unsigned int seed = 0;
	FILE *dev_urandom;
	struct timeval now;

	do {
		dev_urandom = fopen("/dev/urandom", "rb");
	} while (dev_urandom == NULL && errno == EINTR);

	if (dev_urandom) {
		int r;

		setvbuf(dev_urandom, NULL, _IONBF, 0);
		do {
			errno = 0;
			r = fread(&seed, sizeof(seed), 1, dev_urandom);
		} while (errno == EINTR);

		if (r != 1) {
			seed = 0;
		}
		fclose(dev_urandom);
	}

	if (seed == 0) {
		gettimeofday(&now, NULL);
		seed = now.tv_usec;
	}

	return seed;
}

/*
@return	: [0, RAND_MAX]
*/
int
rand_get(void)
{
	unsigned int seed = seed_get();

	srand(seed);

	return rand();
}

int
cmpar(const void *a, const void *b)
{
	struct bucket *_a = (struct bucket *)a;
	struct bucket *_b = (struct bucket *)b;

	return (_a->c - _b->c);
}

int
main(void)
{
	int i;

	struct bucket arr[10];

	for (i = 0; i < NMEMB(arr); i++) {
		arr[i].c = rand_get() % 1000;
		printf("%5d\t", arr[i].c);
	}
	printf("\n");

	qsort(arr, NMEMB(arr), SIZE(arr), cmpar);

	for (i = 0; i < NMEMB(arr); i++) {
		printf("%5d\t", arr[i].c);
	}
	printf("\n");

	return 0;
}