C/c++中关于qsort函数的

参考原文：https://www.cnblogs.com/CCBB/archive/2010/01/15/1648827.html

http://www.cplusplus.com/reference/cstdlib/qsort/

1.函数原型：

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

/*base: 
*Pointer to the first object of the array to be sorted, converted to a *void*. */

/*num:
*Number of elements in the array pointed to by base.
*size_t is an unsigned integral type.
*/
/*size:
*Size in bytes of each element in the array.
*size_t is an unsigned integral type.
*/
/*compar:    
int compar (const void* p1, const void* p2);
*如果返回值<0, p1指向的元素排在p2指向的元素之前
*如果==0，两元素
*返回值>0，p1指向的元素排在p2指向的元素之前
*/

2.使用例子

/* qsort example */
#include <stdio.h>      /* printf */
#include <stdlib.h>     /* qsort */

int values[] = { 40, 10, 100, 90, 20, 25 };

int compare (const void * a, const void * b)
{
  return ( *(int*)a - *(int*)b );
}

int main ()
{
  int n;
  qsort (values, 6, sizeof(int), compare);
  for (n=0; n<6; n++)
     printf ("%d ",values[n]);
  return 0;
}

输出为 :

10 20 25 40 90 100