[英]How to allocate memory to a typedef struct within array of structs
我一直在尝试将 memory 分配给指针变量,但它一直给我错误或分段错误。 如何正确初始化指向课程结构的指针变量?
typedef struct {
char courseId[7];
char courseName[10];
} Course;
struct Student{
char firstName[10];
char lastName[10];
int studentId;
Course *course;
};
int main() {
int numStudents;
printf("How many students do you wish to register?: ");
scanf("%d", &numStudents);
struct Student *student[numStudents];
student[numStudents] = malloc(sizeof(*student[numStudents]));
student[numStudents]->course = malloc(sizeof*(numStudents * Course));
for (int i = 0; i < numStudents; i++) {
printf("Enter student #%d First Name: ", i+1);
scanf("%s", student[i]->firstName);
printf("Enter student Last Name: ");
scanf("%s", student[i]->lastName);
printf("Enter Student ID: ");
scanf("%d", &student[i]->studentId);
printf("Enter Course ID: ");
//student[i]->course = malloc(sizeof(*(student[i]->course)));
scanf("%s", student[i]->course->courseId);
printf("Enter Cousrse Name: ");
//student[i]->course = malloc(sizeof(*(student[i]->course)));
scanf("%s", student[i]->course->courseName);
}
for (int i = 0; i < numStudents; i++) {
printf("Student Name: %s %s\n", student[i]->firstName, student[i]->lastName);
printf("Student ID: %d\n", student[i]->studentId);
printf("Course Code: %s\n", student[i]->course->courseId );
printf("Course name: %s\n", student[i]->course->courseName);
free(student[i]->course);
}
你几乎拥有它,需要进行一些更正。 Student 中的课程 object 不需要是指针。 Student 结构的数组需要动态分配,然后再释放。 ->
用作取消引用运算符,但在您的情况下[]
已经取消引用,因此您将使用.
而不是->
并且当您为结构数组分配 memory 时,它需要是结构的大小乘以结构的数量。 malloc(sizeof(struct Student)*numStudents);
typedef struct {
char courseId[7];
char courseName[10];
} Course;
struct Student{
char firstName[10];
char lastName[10];
int studentId;
Course course;
};
int main() {
int numStudents;
printf("How many students do you wish to register?: ");
scanf("%d", &numStudents);
struct Student* students = malloc(sizeof(struct Student)*numStudents);
for (int i = 0; i < numStudents; i++) {
printf("Enter student #%d First Name: ", i+1);
scanf("%s", students[i].firstName);
printf("Enter student Last Name: ");
scanf("%s", students[i].lastName);
printf("Enter Student ID: ");
scanf("%d", &students[i].studentId);
printf("Enter Course ID: ");
scanf("%s", students[i].course.courseId);
printf("Enter Cousrse Name: ");
scanf("%s", students[i].course.courseName);
}
for (int i = 0; i < numStudents; i++) {
printf("Student Name: %s %s\n", students[i].firstName, students[i].lastName);
printf("Student ID: %d\n", students[i].studentId);
printf("Course Code: %s\n", students[i].course.courseId );
printf("Course name: %s\n", students[i].course.courseName);
}
free(students);
return 0;
}
我试图对您的代码进行最小的更改。
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