Question

我不确定我在这里做错了什么，我只是尝试将一个课程节点添加到具有指定值的链接列表，但是当我尝试打印链表时，它一直说它是空的，我不是确定有什么问题。

我现在一切都在工作，除了当我通过列表的大约1/3时，列表段错误，我不知道为什么。请帮助！

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

 #define MAX 50

 typedef struct courses{
    char *abbr;
    char *name;
    int credits;
    char *prof;
    struct courses *next;
 }courses;

 int isAbbr(char *string);
 int isName(char *string);
 int isCredit(char *string);
 int isProf(char *string);
 int isPre(char *string);
 courses *readfile(FILE *);
 courses *create_course(char *abbr, char *prof, int credits, char *fulldesc);
 courses *create_list(courses *, courses *);
 void Print(courses *);

 int main(int argc, char **argv)
 {
    if (argc != 2)
    {
            printf("Inadequate amount of arguments.\n");
            return 0;
    }
    FILE *fp = fopen(argv[1], "r");
    if (fp == NULL)
    {
            printf("File cannot be opened.\n");
            return 0;
    }

    courses* head = NULL;
    head = readfile(fp);

    Print(head);

    printf("=== task1: construct a linear linked list from the catalog ===\n\n=== task2: user input and producing output ===\n\n");
    int choice = 0;
    while (choice != 3)
    {
            printf("\nSelect your option below:\n1-Register for a Course\n2-See my total\n3-Exit\nChoice: ");
            scanf("%d",&choice);
    }

    printf("\n");
    return 0;
 }

 courses *readfile(FILE *fp)
 {
    courses *head, *entry;
    head = entry = NULL;

    char *abbr = malloc(MAX);
    char *name = malloc(MAX);
    char *prof = malloc(MAX);
    char *desc = malloc(MAX);
    char *fulldesc = malloc(MAX);
    char *fullName = malloc(MAX);

    int credit;
    int credflag = 0;
    int nameFlag = 0;
    int profFlag = 0;
    int preFlag = 0;
    int credits = 0;
    int descflag = 0;

    char line[MAX];
    while (fgets(line, MAX - 1, fp) != NULL)
    {
            if (line[strlen(line) - 1] == '\n')
            {
                    line[strlen(line) - 1] = '\0';
            }
            char* token = strtok(line," ,\t");
            while (token != NULL)
            {
                    if (isAbbr(token) == 1)
                    {
                            abbr = malloc(sizeof(char));;
                            strcpy(abbr, token);
                            credflag = 1;
                            preFlag = 0;
                            profFlag = 1;
                    }
                    if (isName(token) == 1)
                    {
                            if (descflag == 1 && isCredit(token) != 1)
                            {
                                    fulldesc = strcat(desc, token);
                            }
                            else
                            {
                                    desc = malloc(sizeof(char));
                                    strcpy(desc,token);
                                    descflag = 1;
                            }
                    }
                    else
                    {
                            descflag = 0;
                    }
                    if (isCredit(token) == 1 && credflag == 1)
                    {
                                    credits = atoi(token);
                                    credflag = 0;
                                    descflag = 0;
                    }
                    if (isProf(token)== 1 && profFlag == 1)
                    {
                            if(nameFlag == 1 && name[0] != 'T' && token[0] != 'O') 
                            {
                                    prof = strcat(name, token);
                                    entry = create_course(abbr,prof,credits, fulldesc);
                                    head = create_list(head,entry);
                                    profFlag = 0;
                                    nameFlag = 0;
                            }
                            else
                            {
                                    name = malloc(sizeof(char));
                                    strcpy(name, token);
                                    nameFlag = 1;
                            }
                    }
                    else
                    {
                            nameFlag = 0;
                    }
                    token = strtok(NULL," ,\t");
            }
    }
}

courses *create_course(char *abbr, char *prof, int credits, char *fulldesc)
 {
    courses *entry = (courses*)malloc(sizeof(courses));

    //printf("%30s %50s %30s %30d\n",abbr,fulldesc,prof,credits);

    entry->abbr=(char*)malloc(sizeof(char));
    strcpy(entry->abbr, abbr);

    entry->prof=(char*)malloc(sizeof(char));
    strcpy(entry->prof, prof);

    entry->name=(char*)malloc(sizeof(char));
    strcpy(entry->name, fulldesc);

    entry->credits = credits;
    entry->next = NULL;

    return entry;
 }

courses *create_list(courses *head, courses *entry)
{
    if (head == NULL)
    {
            return entry;
    }
    courses* curr = head;
    while (curr->next != NULL)
    {
            curr = curr->next;
    }
    curr->next = entry;

    return head;
}

void Print(courses *head)
{
    if(head == NULL)
    {
            printf("Course list is empty\n\n");
            return;
    }
    printf("\n");
    while(head)
    {
            printf("%20s %20d\n",head->abbr,head->credits);
    }
    printf("\n\n");
}

 int isName(char *string)
 {
    int length = strlen(string);
    int i;
    if (isupper(string[0]))
    {
            for (i=1; i<length; i++)
            {
                    if (isupper(string[i]) || string[i] == ':')
                    {
                            continue;
                    }
                    else
                    {
                            return 0;
                    }
            }
            return 1;
    }
    return 0;
 }

int isPre(char *string)
{
    int length = strlen(string);
    int i;
    if (length == 14)
    {
            printf("\t%s\n",string);
            return 1;
    }
    return 0;
}

int isProf(char *string)
{
    int length = strlen(string);
    int i;
    if (isupper(string[0]))
    {
            for (i=1; i<length; i++)
            {
                    if (islower(string[i]))
                    {
                            continue;
                    }
                    else
                    {
                            return 0;
                    }
            }
            return 1;
    }
    return 0;
}

int isCredit(char *string)
{
    int n;
    int nfields = sscanf(string, "%d", &n);
    if (nfields == 1)
    {
            return 1;
    }
    return 0;
}

 int isAbbr(char *string)
 {
    int length = strlen(string);
    if (length == 8 && string[4] == '-')
    {
            //printf(" %s\n",string);
            return 1;
    }
    return 0;
 }

Answer 1

学习使用像GDB这样的调试器。找到这样的bug变得微不足道。由于这是一个链表，我认为这是你课程的第一个作业。来到StackOverflow并等待您遇到的每一个错误的答案都不起作用。

每个程序员都需要知道如何使用调试器。没有人，你将无法通过学校。

C程序不会在链表中打印节点

1 个答案: