qsort函数专题

# define _CRT_SECURE_NO_WARNINGS 
#include <stdio.h>
#include <stdlib.h>     /* qsort */
int int_cmp(const void* p1, const void* p2)
{
  return (*(int*)p1 - *(int*)p2);//将void*类型转化为int*类型，并将其解引用
}
int main()
{
  int arr[] = { 1, 3, 5, 7, 9, 2, 4, 6, 8, 0 };
  int i = 0;
  qsort(arr, sizeof(arr) / sizeof(arr[0]), sizeof(int), int_cmp);//(首元素地址，元素个数，字节数，比较函数)
  for (i = 0; i < sizeof(arr) / sizeof(arr[0]); i++)
  {
    printf("%d ", arr[i]);
  }
  printf("\n");
  return 0;
}

# define _CRT_SECURE_NO_WARNINGS 
#include <stdio.h>
#include <stdlib.h>     /* qsort */
struct Stu
{
  char name[20];
  int age;
};
int cmp_by_age(const void* e1, const void* e2)
{
  return ((struct Stu*)e1)->age - ((struct Stu*)e2)->age;
}
void test()
{
  struct Stu s[] = { {"zhangsan",20},{"lisi",19},{"wangwu",30} };
  int sz = sizeof(s) / sizeof(s[0]);
  qsort(s, sz, sizeof(s[0]), cmp_by_age);
}
int main()
{
  test();
  return 0;
}

# define _CRT_SECURE_NO_WARNINGS 
#include <stdio.h>
#include <stdlib.h>     /* qsort */
#include<string.h>
struct Stu
{
  char name[20];
  int age;
};
int cmp_by_name(const void* e1, const void* e2)
{
  return strcmp(((struct Stu*)e1)->name, ((struct Stu*)e2)->name);
}
void test()
{
  struct Stu s[] = { {"zhangsan",20},{"lisi",19},{"wangwu",30}};
  int sz = sizeof(s) / sizeof(s[0]);
  qsort(s, sz, sizeof(s[0]), cmp_by_name);
}
int main()
{
  test();
  return 0;
}

# define _CRT_DEFINE_NO_WARNINGS 
#include <stdio.h>
#include <stdlib.h>     /* qsort */
#include<string.h>
int int_cmp(const void* p1, const void* p2)
{
  return (*(int*)p1 - *(int*)p2);
}
void swap(void* p1, void* p2, int size)
{
  int i = 0;
  for (i = 0; i < size; i++)
  {
    char tmp = *((char*)p1 + i);
    *((char*)p1 + i) = *((char*)p2 + i);
    *((char*)p2 + i) = tmp;
  }
}
void bubble(void* base, int count, int size, int(*cmp)(void*, void*))
{
  int i = 0;
  int j = 0;
  for (i = 0; i < count - 1; i++)//冒泡排序
  {
    for (j = 0; j < count - i - 1; j++)
    {
      if (cmp((char*)base + j * size, (char*)base + (j + 1) * size) > 0)
      {
        swap((char*)base + j * size, (char*)base + (j + 1) * size, 4);
      }
    }
  }
}
int main()
{
  int arr[] = { 1, 3, 5, 7, 9, 2, 4, 6, 8, 0 };
  int i = 0;
  bubble(arr, sizeof(arr) / sizeof(arr[0]), sizeof(int), int_cmp);
  for (i = 0; i < sizeof(arr) / sizeof(arr[0]); i++)
  {
    printf("%d ", arr[i]);
  }
  return 0;
}