相关疑难解决方法(0)

qsort(bt->rw[t], bt->num[t], 
      sizeof(TRELLIS_ATOM *), 
      (int (*)(const void *,const void *))compare_wid);

bt->rw[t]是一个指向struct指针的指针,bt->[num]是一个int,我不明白第四个参数是什么,除了compare_wid是在某处定义的函数,如下所示:

static int compare_wid( TRELLIS_ATOM* a, TRELLIS_ATOM* b )
{
   ...
   return x;
}

我正在尝试让程序读取一个文本文件,其中包含"1001姓氏姓氏10 20 30"等信息,学生人数,姓名,姓氏和3年级.这是我的代码:

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

 struct Student {
     int number;
     char name[30];
     char surname[30];
     int midterm1,midterm2,midterm3;
 } Student;

 int comp(const void * aa, const void * bb)
 {
    struct Student a = *(struct Student*)aa;
    struct Student b = *(struct Student*)bb;
    if (a.midterm1==b.midterm1)
            return 0;
    else if (a.midterm1 < b.midterm1)
            return -1;
    else
            return 1;
  } // comp


  int main(void)
  {
      int choice,studentnumber,midterm1,midterm2,midterm3,i,n;
      char surname;
      FILE *cfPtr;

      struct student *name;
      name = malloc( 10 * sizeof(Student));

      if …