c - 结构数组的排序成员

Question

给定一个结构数组(在 C 中)，我试图按性别分组并按数字顺序按子顺序打印结果。例如:

struct employee{
char gender[13]
char name[13];
int id;
};

假设我这样定义结构数组:

struct employee info[2]={{"male","Matt",1234},{"female","Jessica",2345},{"male","Josh",1235}};

我怎样才能像这样打印结果

1234 Matt
1235 Josh


2345 Jessica

Answer 1

您需要实现一个排序函数，根据需要比较结构

int compare(const void *s1, const void *s2)
{
  struct employee *e1 = (struct employee *)s1;
  struct employee *e2 = (struct employee *)s2;
  int gendercompare = strcmp(e1->gender, e2->gender);
  if (gendercompare == 0)  /* same gender so sort by id */
    return e1->id - e2->id;
  else
    return -gendercompare;  /* the minus puts "male" first as in the question */
}

然后使用标准库中的 qsort。

qsort(data, count, sizeof(struct employee), compare);

在比较函数中，您可能想要检查 id 是否相等，然后您可以根据需要按名称排序(也可以使用 strcmp())。

编辑:刚刚编译并修复了它。这是一个小测试程序

    #include <stdio.h>
    #include <stdlib.h>

    struct employee{
      char gender[13];
      char name[13];
      int id;
    };

    int compare(const void *s1, const void *s2)
    {
      struct employee *e1 = (struct employee *)s1;
      struct employee *e2 = (struct employee *)s2;
      int gendercompare = strcmp(e1->gender, e2->gender);
      if (gendercompare == 0)  /* same gender so sort by id */
        return e1->id - e2->id;
      else
        return -gendercompare;
    }

    main()
    {
      int i;
      struct employee info[]={{"male","Matt",1234},{"female","Jessica",2345},{"male","Josh",1235}};

      for (i = 0; i < 3; ++i)
        printf("%d\t%s\t%s\n", info[i].id, info[i].gender, info[i].name);

      qsort(info, 3, sizeof(struct employee), compare);

      for (i = 0; i < 3; ++i)
        printf("%d\t%s\t%s\n", info[i].id, info[i].gender, info[i].name);
    }

输出:

$ ./a.exe
1234    male    Matt
2345    female  Jessica
1235    male    Josh
1234    male    Matt
1235    male    Josh
2345    female  Jessica