Question

//Good day. This is just a part of my source code. My main predicament is that the print_list function only prints the first input of the user in the linked list. I can’t seem to pin point the problem as the logic of the function seems right. The insert_list function seems to work fine too but I’m not that sure.

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

//this is the node

typedef struct node
{
        char name[61];
        int month;
        int day;
        int year;
        struct node *next;
}node;

//this is the list

typedef struct list
{
        node *head;
        node *tail;
}list;

//this creates the node by accepting the user’s input and puts them in the node

node *create_node()
{
        int x;
        node *data = (node*) malloc(sizeof(node));
        printf("Name: ");
        fgets(data->name, 61, stdin);
        printf("Birthdate (mm/dd/yyyy): ");
        scanf("%d%*[/]%d%*[/]%d", &data->month, &data->day, &data->year);
        getchar();
        if ((data->month)==0||(data->month)>=13||(data->day)<=0||(data->day)>=32||(data->year)<=1977||(data->year)>=3001)
        {
                while ((data->month)==0||(data->month)>=13||(data->day)<=0||(data->day)>=32||(data->year)<=1977||(data->year)>=3001)
                {
                        printf("Invalid Input.\n");
                        printf("Please Enter a Valid Birthdate(mm/dd/yyyy): \n");
                        scanf("%d%*[/]%d%*[/]%d", &data->month, &data->day, &data->year);
                        getchar();
                }
        }
        printf("******************************************************************\n");
        for (x=0; x<=strlen(data->name); x++)
        {
            if (data->name[x]=='\n')
            {
                    data->name[x]='\0';
            }
    }
    printf("Birthday reminder for %s is added.\n", data->name);
    return data;
}


list *create_list(list *plist)
{
        plist->head = NULL;
        plist->tail = NULL;
        return plist;
}

//this inserts the node in the list

list *insert_list(list *plist, node *pnode, node *new_node)
{
    if(plist->head==NULL)
    {
            plist->head=new_node;
            new_node->next=NULL;
    }
    else
    {
            new_node->next = NULL;
            pnode->next = new_node;
            plist->tail = new_node;
    }
    return plist;
}

//this prints the list

list *print_list(list *plist)
{
        node *current = plist->head;
        int i;
        for(i=1;current!=NULL;i++)
        {    
            printf("[%d] %s\n",i ,current->name);
            printf("Birth Date: %d/%d/%d\n", current->month, current->day, current->year);
            current=current->next;
    }
}

//this deallocates the list

list *free_list(list *List)
{
    node *current = List->head;
    node *temp = NULL;
    while(current != NULL)
    {
            temp = current;
            current = current->next;
            free(temp);
    }

    List->head = NULL;
    List->tail = NULL;
}

//this is the main

int main(void)
{
        list* List = (list*) malloc(sizeof(list));
        List = create_list(List);
        char x;
        node *data = (node *) malloc(sizeof(node));
        printf("******************************************************************\n");
        printf("                    ADD BIRTHDAY REMINDER FORM\n");
        printf("******************************************************************\n");
        List = insert_list(List, data, create_node(data));
        printf("Would you like to add another(y/n)?\n");
        scanf("%c", &x);
        if (x=='y')
        {
                while (x=='y')
                {
                        if (x=='y')
                        {
                                getchar();
                            printf("******************************************************************\n");
                                node *data = (node *) malloc(sizeof(node));
                                List = insert_list(List, data, create_node(data));
                                printf("Would you like to add another(y/n)?\n");
                                scanf("%c", &x);
                        }
                }
        }
    print_list(List);
    free(List);
    return 0;

}

//this code is ready for compilling

Answer 1

I do not understand, what do you intend by pnodein insert_list, and I guess, there is the error. Probably, you mean something like previous node. However, the tail is already the previous node. In addition, you use an empty node there, even you alloc memory for a node in create_node. Maybe, the following code would be more appropriate:

list *insert_list(list *plist, node *new_node)
{
    if(plist->head==NULL)
    {
            plist->head=new_node;
            plist->tail=new_node;
            new_node->next=NULL;

    }
    else
    {
            new_node->next = NULL;
            plist->tail->next = new_node;
            plist->tail = new_node;
    }
    return plist;
}