在C语言中，我如何从文本文件中读取数据并将其插入一个链接列表，该链接列表根据名字按升序排列？

Question

The text file "mh.txt" includes the following names, surnames, gender and birth date of 3 people separated by semicolons.

which look like this:

Tiffany;Evans Smith;F;22/01/1989;

Alex;Williams;M;23/06/1988;

Clay;Bristol;F;30/12/1989;

I want to store every person's details in a node so we'd have 3 nodes in total. All connected in a linked list. Then I want to print the linked list using a print function.

The problem is that my compiler displays the message "fix.exe has stopped working" every time I compile and run! my c file is called fix.c

This is my attempt:

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


#define FALSE 0
#define TRUE 1

#define SIZE 100

struct Node{

    char  fname[SIZE];
    char sname[SIZE];
    char gender;
    char Byear[SIZE];
    struct Node *next;
};

struct ListRecord
{
    struct Node *head;
    struct Node *tail;
    int size;
};
typedef struct ListRecord List;

List* CreateList(void);
void MakeEmptyList(List *);
void printFriends(List *);
List * initialiseFL(List *);

int main(){

    List *myList;
    int option;
    int exit=FALSE;
    char fname[SIZE];

    myList = CreateList();

    myList=initialiseFL(myList);//reads data from text file and adds nodes 
to linked list




    while(!exit){

        fflush(stdin);
        printf("C:>FriendBook friends.txt\n");
        printf("Your FriendBook has been created.\n");
        printf("(1) Insert a new friend\n");
        printf("(2) Print your friends\n");
        printf("(3) Search for your friend\n");
        printf("(4) Block your friend\n");
        printf("(5) Print your blocked friend\n");
        printf("(6) Exit\n");
        printf("Enter your option:");
        printf("\n\n");
        scanf("%d",&option);
        fflush(stdin);

        switch(option){

            case 2:
                printFriends(myList);
                break;

            default:
                printf("Command not recognised!!\n");
                break;

        }
    }


    return 0;
}


List* CreateList(){

    List *l;

    l = (struct ListRecord *) malloc(sizeof(struct ListRecord));
    if (l == NULL)
        printf("Out of memory!\n");

    MakeEmptyList(l);

    return l;
 }

void MakeEmptyList(List *l)
{
    l->head = (struct Node *) malloc(sizeof(struct Node));
    if (l->head == NULL)
        printf("Out of memory!\n");

    l->head->next = NULL;
    l->tail = l->head;
    l->size = 0;
}
List* initialiseFL(List *l){


    FILE *IN;

    IN =fopen("mh.txt", "r");

    if (IN == NULL){
        printf("Could not open text file!!\n");
    }

    while((fgetc(IN))!=EOF){

        struct Node *p;
        p=(struct Node*) malloc(sizeof(struct Node));

        char temp;
        temp=fgetc(IN);

        int i=0;

        //read first name a char at a time until ;
        while(temp!=';'){

            p->fname[i]=temp;
            i++;
            temp=fgetc(IN);
         }
         p->fname[i]='\0';


         //read second name a char at a time until ;
         temp=fgetc(IN);    
         i=0;   
         while(temp!=';'){

             p->sname[i]=temp;
             i++;
             temp=fgetc(IN);
         }
         p->sname[i]='\0';


         //read gender from text file
         temp=fgetc(IN);    
         p->gender=temp;

         //read birth year from text file
         temp=fgetc(IN);    
         temp=fgetc(IN);    
         i=0;   
         while(temp!=';'){

            p->Byear[i]=temp;
            i++;
            temp=fgetc(IN);
        }
        p->Byear[i]='\0';



        //if list is empty, add node right after the dummy
        if (l->size==0){
            l->head->next=p;
            l->tail=p;
            l->size++;
        }

         //if the list contanins one node after the dummy
         struct Node *first;
         first=l->head->next;
         if(l->size==1){
            if(strcmp(p->fname[0],first->fname[0])>0 && first->next==NULL){
                p->next=NULL;
                first->next=p;
                l->tail=p;
                l->size++;
            }
            else{
                 p->next=first;
                 l->head->next=p;
                 l->size++;
                 first=l->head->next;//reset "first" to point to the 1st 
node in the list
            }
         }


         struct Node *second;
         second=first->next;

         //if it is to be added at the beginning 
        if(l->size>=2){
            if(strcmp(p->fname[0],first->fname[0])<0){
                p->next=first;
                l->head->next=p;
                l->size++;
                first=l->head->next;//reset "first" to point to the 1st node 
in the list
             }

             else{
                while(!(strcmp(p->fname,first->fname)>0 && strcmp(p-
>fname,second->fname)<0 )){
                    first=first->next;
                    second=second->next;
                }
                if(second->next==NULL){
                    p->next=NULL;
                    first->next=p;
                }
                else{
                    p->next=second;
                    first->next=p;
                }

                first=l->head->next;//reset "first" to point to the 1st node 
in the list
                second=first->next;//reset "second" to point to the 2st node 
in the list
                }



        }

        }
    fclose(IN);


    return l;
}

 void printFriends(List *l){


    //make a temp head that points to the dummy
    struct Node *temp;
    temp=(struct Node*) malloc(sizeof(struct Node));
    temp=l->head->next;

    printf("Your friends are listed below.\n");
    printf("Name\tSurname\tGender\tBirth Year\n");


     while(temp!=NULL){
         printf("%s\t%s\t%c\t%s\n",temp->fname,temp->sname,temp-
>gender,temp->Byear);
        temp=temp->next;
    }

}

Answer 1

consider one of the statement of your code

if(strcmp(p->fname[0],first->fname[0])<0){

strcmp() excepts both arguments as strings , but p->fname[0] will result in single character , just modify as below.

  if(strcmp(p->fname,first->fname)<0){

And there is bug in below code, you are updating first & second not p thats why loop is running infinitely.

while(!(strcmp(p->fname,first->fname)>0 && strcmp(p->fname,second->fname)<0 )){

    first=first->next;
    second=second->next;
                                }

I hope it will helps.

Answer 2

You can use the code below for your requirement.

What is char Byear[SIZE]; this field? As per your data file, it should be a date field and as forth field in data file is a date.

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

    struct Friend
    {
            char  *name;
            char  *sur;
            char  *gen;
            char  *date;
            struct Friend *next;
    };

    struct Friend * initializeFL(char *);
    void printFriends(struct Friend *);

    int main()
    {
            printf("\nsdasda\n");
            struct Friend *head;
            char fname[100];
            printf("Enter the name of file .txt:  \t");
            gets(fname);
            head=initializeFL(fname);
            printFriends(head);
    }

    struct Friend * initializeFL(char *fname)
    {
            FILE* fpointer;
            char ch;
            fpointer = fopen(fname,"r");
            if(fpointer == NULL)
            {

                do
                {
                    printf("\nFile not found, please enter the name of file again: \t");
                    gets(fname);
                    fpointer = fopen(fname,"r");
                }while(fpointer == NULL);
            }

            //FILE IS OPENED
            struct Friend *head=NULL;
            struct Friend *t, *p, *q;
            char line[255];
            char sent[2]=";";

            while(!feof(fpointer) && fgets(line,sizeof line,fpointer))
            {
                char *name=strtok(line,sent);
                char *sur=strtok(NULL,sent);
                char *gen=strtok(NULL,sent);
                char *date=strtok(NULL,sent);
                    if(head == NULL)
                    {
                              head=(struct Friend*)malloc(sizeof(struct Friend));
                              t = head;
                              t->name = (char *)malloc(strlen(name));
                              t->sur = (char *)malloc(strlen(sur));
                              t->gen = (char *)malloc(strlen(gen));
                              t->date = (char *)malloc(strlen(date));
                              strcpy(t->name,name);
                              strcpy(t->sur,sur);
                              strcpy(t->gen,gen);
                              strcpy(t->date,date);
                              t->next=NULL;
                    }
                    else
                    {
                            p=(struct Friend*)malloc(sizeof(struct Friend));
                            p->name = (char *)malloc(strlen(name));
                            p->sur = (char *)malloc(strlen(sur));
                            p->gen = (char *)malloc(strlen(gen));
                            p->date = (char *)malloc(strlen(date));
                            strcpy(p->name,name);
                            strcpy(p->sur,sur);
                            strcpy(p->gen,gen);
                            strcpy(p->date,date);
                            p->next=NULL;
                            q = t = head;
                            int i = strcmp(p->name,t->name);
                            printf("i = %d\n",i);
                            while(t!=NULL && strcmp(p->name,t->name)> 0)
                            {
                              q = t;
                              t=t->next;
                            }
                            if(t == head)
                            {
                              p->next=head;
                              head=p;
                            }
                            else
                            {
                              q->next = p;
                              p->next = t;
                            }
                     }
            }
            return head;
    }

    void printFriends(struct Friend *head)
    {
            while(head!=NULL)
            {
                    printf("Name :%s\n",head->name);
                    printf("Surname :%s\n",head->sur);
                    printf("Name :%s\n",head->gen);
                    printf("Name :%s\n",head->date);
                    head=head->next;
            }
    }