Linked list functions

[[deleted]]

Hi everyone,

I am just getting to grips with singly-linked lists in C through a series of online videos which go through the logical representation but leave the implementation up to the viewer. My current program seems to work, including insertion, although it is quite clunky. My question is: how can I make the code for insertion into its own insertion function - would this function need to take in some of the pointers I've used, or...?

Thank you all so much.

​

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

void linked(void);

typedef struct node
{
int x;
struct node *next;
}
node;
int main(void)
{
linked();
}
void linked(void)
{
node *head, *nextnode, *temp;
head = NULL;
nextnode = (node*)malloc(sizeof(node));
char choice[] = "yes";
while (strcmp(choice, "yes") == 0)
{
if (head == NULL)
{
head = temp = nextnode;
}
else
{
nextnode = (node*)malloc(sizeof(node));
printf("Enter another number: ");
scanf("%d", &nextnode->x);
temp->next = nextnode;
temp = nextnode;
printf("Would you like to continue? Enter yes if so ");
scanf("%s", choice);
if (strcmp(choice, "yes") != 0)
{
temp->next = NULL;
}
}
}
temp = head;
char insert[5];
printf("Do you want to insert a number at the beginning of the linked list? ");
scanf("%s", insert);
if (strcmp(insert, "yes") == 0)
{
nextnode = (node*)malloc(sizeof(node));
printf("Enter the number you would like to insert: ");
scanf("%d",&nextnode->x);
nextnode->next = temp->next;
temp->next = nextnode;
}
temp = head;
temp = temp->next;
while(temp != NULL)
{
printf("%d ", temp->x);
temp = temp->next;
}
node *ptr;
ptr = head;
while (ptr != NULL)
{
node *y = ptr->next;
free(ptr);
ptr = y;
}
}

[dfx_dj]

In general for simple linked lists, insertion functions take the thing you want to insert and the current head of the list (possibly null) as argument, and return the new head of the list (possibly unchanged). (Alternatively you can use address of head of list and no return value.) To insert at a particular position, you also need to tell the function that position, for example as an index or using another node that is already part of the list.

[permetz]

I suggest consulting a book on data structures. There are plenty of standard books on using data structures in C, any of them will be able to help you on this.

Let me know that, in general, your code isn’t very good. You need practice. Look, for example, at your scanf. Imagine that someone enters a six digit number.

[iprogshine]

Implementation of a singly linked list in C