运行下面的代码后，我得到输出
NAME ：（空）| GPA：0.000000 |年：（空）
链接列表执行不正确吗？我目前正在使用一个makefile，并引入一个名称为gpa和senior / ect的test.data文件。
Ollie 2.9新生
约翰3.2年长
朱莉2.2新生
乔1.8新生
玛丽3.8高级版
苏3.4初级
简2.7高级
鲍勃2.8高级
弗雷德3.2新生
比尔3.3初中
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include "students.h"
Student *top = NULL;
Student *temp, *temp1, *temp2;
// Creates the entire linked list from the file.
// Should call readNext and push
// Returns head of the linked list
Student *buildStudentList()
{
Student *p;
p = readNext();
push(&top, p);
return top; //TODO: Change return
}
//Read a single line from standard input and return a student structure located on the heap
Student *readNext()
{
Student *s =(Student*) malloc(sizeof(Student));
scanf("%s", s -> name);
scanf("%f", &s -> gpa);
scanf("%s", s -> year);
s->next = NULL;
return s; //TODO: Change return
}
//Return a student structure stored on the heap
Student *makeStudent(char *name, float gpa, char *year)
{
Student *s =(Student*) malloc(sizeof(Student));
s -> name = name;
s -> gpa = gpa;
s -> year = year;
s -> next = NULL;
return s; //TODO: Change return
}
//insert a new student node at the head of the linked list
void push(Student **list, Student *student)
{
top = *list;
student -> next = top;
top = student;
}
//Insert a student node in the desired position on the linked list
void insert(Student *list, Student *s, int position)
{
int i;
top = list;
temp = top;
for(i = 1; i < position -1; i++)
{
temp = temp -> next;
}
if(temp == NULL)
{
//blank
}
else
{
s -> next = temp -> next;
temp -> next = s;
}
}
//Displays contents of a single student structure
void display(Student *s){
printf("NAME:%s | GPA: %f | YEAR:%s
", s -> name, s-> gpa, s -> year);
}
//Displays contents of the entire linked list
void displayAll(Student *list)
{
temp = list;
while(temp != NULL)
{
display(temp);
temp = temp -> next;
}
}
//Delete all data allocated on the heap before terminating program
void cleanUp(Student *list)
{
temp1 = list;
temp2 = temp1 -> next;
while(temp1 != NULL)
{
free(temp1);
temp1 = temp2;
}
if(temp2 != NULL)
{
temp2 = temp2 -> next;
}
}
//Main function tests your functions.
int main()
{
printf("Program Started
");
//Construct Linked List from Standard Input
Student *list = buildStudentList();
//Insert a new student in desired position
Student *s = makeStudent("Max",3.0, "senior");
insert(list, s, 3);
//Display entire linked list
displayAll(list);
//Free all heap memory
cleanUp(list);
printf("Program Successful Exit
");
exit(EXIT_SUCCESS);
}
答案 0 :(得分：0)
由于您没有发布struct定义，因此我不得不猜测name是char *name;还是（例如char name[100];）。在代码中，它用作指针。
所以...
您的readNext和makeStudent没有为字符串（char *指针）name和year分配空间，因此它们可能存在段错误。
insert在确实需要Student *list时使用Student **list。
IMO，您应该使用单独的List类型以避免混淆（它具有单个元素：Student *head;）。因此，无论您有Student *list，将其替换为List *list
执行此操作时，当您指的是列表时，不必向下传递Student ** [双星]指针。与list->head相比，使用*list更加容易，而且更具描述性。
也要保持一致。如果某些函数修改列表[它们有要]，则会使用Student **list。其他人使用Student *list，但它们也应保持一致。
不需要各种 global 范围临时变量。这些应在函数范围内使用，并使用更具描述性的名称。
您的insert有问题。如果找不到 位置匹配项（例如，在您的示例中的位置99处插入），它将孤立个节点尝试插入。通常是在尾部插入或返回错误代码。另外，由于您拥有的代码，position的含义[对我来说]还不十分清楚。可能是“在第N个节点之前插入”或“在第N个节点之后插入”。
您不能在双引号字符串中插入文字换行符。因此，请使用\n转义序列（例如）printf("hello world\n");
此外，采用 no 参数的函数应使用void（例如）而不是int main()，而应使用int main(void)。
这是您代码的清理版本，其中包含我上面提到的内容：
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
//#include "students.h"
typedef struct student Student;
struct student {
Student *next;
float gpa;
char *name;
char *year;
};
typedef struct list {
Student *head;
} List;
//insert a new student node at the head of the linked list
void
push(List *list, Student *student)
{
student->next = list->head;
list->head = student;
}
//Return a student structure stored on the heap
Student *
makeStudent(char *name, float gpa, char *year)
{
Student *s = (Student *) malloc(sizeof(Student));
s->name = strdup(name);
s->gpa = gpa;
s->year = strdup(year);
s->next = NULL;
return s;
}
//Read a single line from standard input and return a student structure located on the heap
Student *
readNext(void)
{
char name[1000];
float gpa;
char year[1000];
Student *s = NULL;
int count = scanf("%s %f %s",name,&gpa,year);
if (count == 3) {
printf("readNext: name='%s' gpa=%g year='%s'\n",name,gpa,year);
s = makeStudent(name,gpa,year);
}
return s;
}
// Creates the entire linked list from the file.
// Should call readNext and push
// Returns head of the linked list
List *
buildStudentList(List *list)
{
Student *p;
while (1) {
p = readNext();
if (p == NULL)
break;
push(list, p);
}
return list;
}
//Insert a student node in the desired position on the linked list
int
insert(List *list, Student *s, int position)
{
Student *cur;
Student *prev;
int i;
int goflg;
//position -= 1;
#if 0
i = 1; // insert before Nth position
#else
i = 0; // insert after Nth position
#endif
prev = NULL;
for (cur = list->head; (cur != NULL) && (i < position);
++i, cur = cur->next) {
prev = cur;
}
// this may not be needed -- usual is to insert at tail if position is not
// found -- this will orphan the node to be inserted
#if 0
goflg = (i == position);
#else
goflg = 1;
#endif
if (goflg) {
s->next = cur;
if (prev != NULL)
prev->next = s;
else
list->head = s;
}
return goflg;
}
//Displays contents of a single student structure
void
display(Student *s)
{
printf("NAME:%s | GPA: %f | YEAR:%s\n", s->name, s->gpa, s->year);
}
//Displays contents of the entire linked list
void
displayAll(List *list)
{
Student *temp = list->head;
while (temp != NULL) {
display(temp);
temp = temp->next;
}
}
//Delete all data allocated on the heap before terminating program
void
cleanUp(List *list)
{
Student *cur;
Student *next;
for (cur = list->head; cur != NULL; cur = next) {
next = cur->next;
free(cur->name);
free(cur->year);
free(cur);
}
list->head = NULL;
}
//Main function tests your functions.
int
main(void)
{
List top = { NULL };
List *list;
printf("Program Started\n");
//Construct Linked List from Standard Input
list = buildStudentList(&top);
//Insert a new student in desired position
Student *s = makeStudent("Max", 3.0, "senior");
insert(list, s, 3);
//Display entire linked list
displayAll(list);
//Free all heap memory
cleanUp(list);
printf("Program Successful Exit\n");
exit(EXIT_SUCCESS);
}