Thread: Help with linked lists/ pointers

Thanks for all of the replies. I see what you guys mean about the form it is in and have changed the code so that it shouldn't be as confusing. Here is the changed code:

Code:

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

typedef struct node {
  int value;
  struct node *next;
} node;

void createNewNode(node *head, node *newNode);
void printList(node *head);

int main(int argc, const char * argv[]) {
    node *first;
    first = malloc(sizeof(node));
    node *newNode;
    newNode = malloc(sizeof(node));
    int numberOfEntries = 0;

    first->next = NULL;

    printf("Number of Entries: ");
    scanf("%d", &numberOfEntries);
    printf("\n");

    if(numberOfEntries == 1) {
        printf("Enter Value: ");
        scanf("%d", first->value);
        printf("\n");
    } else {
        int i = 0;
        while(i < numberOfEntries) {
            printf("Enter Value: ");
            scanf("%d", first->value);
            printf("\n");

            createNewNode(first, newNode);
            i++;
        }
    }
    printList(first);

    return 0;
}

void createNewNode(node *head, node *newNode) {
    newNode->next = head;
    head = newNode;
}

void printList(node *head) {
    node *current;
    current = malloc(sizeof(node));
    current = head;

    while(current->next != NULL) {
        printf("Entry: %d\n", current->value);
        current = current->next;
    }

    printf("Entry: %d\n", current->value);

    free(current);
}

I am still pretty lost with what else is wrong with the code.... Linked lists are confusing the hell out of me lol

Here's a little thing that might cause a problem:

Code:

scanf("%d", &first->value);

Again, this is a value vs. reference issue; scanf expects an address reference, so use the &address of operator.

It's not that the printList while loop isn't executing, it's that createNewNode doesn't work. Also, why do you have a malloc call in printList()? Malloc allocates memory for a node -- that is part of what is missing in createNewNode.

You do not need to create more than one *node in main(), namely "head", and malloc it there. No matter what, for the first entry, use that one. For the subsequent ones, you pass the head to createNewNode, which malloc's a new node and set's the last node's next to that:

Code:

void createNewNode(node *head, int val) {
	node *new = malloc(sizeof(node)), *cur=head;
	new->value = val;
	while (cur->next) cur=cur->next;
	cur->next=new;
}

So now your main should look something like this:

Code:

   node *first = malloc(sizeof(node));
    int numberOfEntries = 0, value;
	int i = 0;

    printf("Number of Entries: ");
    scanf("%d", &numberOfEntries);
    printf("\n");

	printf("Enter Value: ");
	scanf("%d", &first->value);
	printf("\n");
        while(i < numberOfEntries-1) {
            printf("Enter Value: ");
            scanf("%d", &value);
            printf("\n");

            createNewNode(first,value);
            i++;
        }

Zlatko, becasue of issue #5 above, uses a pointer to a pointer (**) to accomplish the same thing, you may find my method somewhat simpler and easy to understand (or it may be the other way around).

@tabstop: my point was the unorthodox typedef'ing is the first mistake that needs correcting. Neither I nor you nor anyone else will want to correct the OP while maintaining that.