LinkedList length, access and implementation via a heap. C - c

Question

I am trying to print the length of a linked list I created in another .c file called linklist.c from the main.c file. It is not working and I believe is has something to do with pointers and/or memory management over all. I call into question the heap mainly here. some guidance would be appreciated.
#include <stdio.h>
#include <stdlib.h>
#include "node.h"
int main()
{
printf("Hello world!\n");
struct node* mylist = BuildOneTwoThree();
int length = Length(mylist);
printf(mylist->data);
printf(length);
return 0;
}
#include "node.h"
#include <stdio.h>
#include <stdlib.h>
// Return the number of nodes in a list (while-loop version)
int Length(struct node** head) {
int count = 0;
struct node* current = head;
while (current != NULL) {
count++;
current = current->next;
}
return(count);
}
/*
Build the list {1, 2, 3} in the heap and store
its head pointer in a local stack variable.
Returns the head pointer to the caller.
*/
struct node* BuildOneTwoThree() {
struct node* head = NULL;
struct node* second = NULL;
struct node* third = NULL;
head = malloc(sizeof(struct node)); // allocate 3 nodes in the heap
second = malloc(sizeof(struct node));
third = malloc(sizeof(struct node));
head->data = 1; // setup first node
head->next = second; // note: pointer assignment rule
second->data = 2; // setup second node
second->next = third;
third->data = 3; // setup third link
third->next = NULL;
// At this point, the linked list referenced by "head"
// matches the list in the drawing.
return head;
}
/*
Takes a list and a data value.
Creates a new link with the given data and pushes
it onto the front of the list.
The list is not passed in by its head pointer.
Instead the list is passed in as a "reference" pointer
to the head pointer -- this allows us
to modify the caller's memory.
*/
void Push(struct node** headRef, int data) {
struct node* newNode = malloc(sizeof(struct node));
newNode->data = data;
newNode->next = *headRef; // The '*' to dereferences back to the real head
*headRef = newNode; // ditto head points to new node
}
// Given a list and an index, return the data
// in the nth node of the list. The nodes are numbered from 0.
// Assert fails if the index is invalid (outside 0..lengh-1).
int GetNth(struct node* head, int index) {
struct node* current = head;
int answer = 0;
int x = index;
if(x <= 0 || x >= sizeof(head)-1 )
{
return -1;
}
for(int i = 0; i <= sizeof(head)-1; i++){
if (i == x){
return current->data;
}
current = current->next;
}
}
As you can see I use the BuildOneTwoThree function to build the linkedlist and am writing appropriate functions...It crashes when I try to access mylist into output.

Answer 1

For the most part the code seems to function from the point of view of the question only, printf had to be properly formatted.
printf("%i", length);

Answer 2

type cast malloc required
Change **head to *head in function argument Length
Use proper printf statement.
This question is limited to printing lenght of link list. please find code below:
#include <stdio.h>
#include <stdlib.h>
struct node
{
int data;
struct node *next;
};
struct node* BuildOneTwoThree();
int Length(struct node* head);
int main()
{
printf("Hello world!\n");
struct node* mylist = BuildOneTwoThree();
int length = Length(mylist);
printf("data =%d\n",mylist->data);
printf("length = %d",length);
return 0;
}
// Return the number of nodes in a list (while-loop version)
int Length(struct node* head) {
int count = 0;
struct node* current = head;
while (current != NULL) {
count++;
current = current->next;
}
return(count);
}
/*
Build the list {1, 2, 3} in the heap and store
its head pointer in a local stack variable.
Returns the head pointer to the caller.
*/
struct node* BuildOneTwoThree() {
struct node* head = NULL;
struct node* second = NULL;
struct node* third = NULL;
head = (struct node *)malloc(sizeof(struct node)); // allocate 3 nodes in the heap
second = (struct node *)malloc(sizeof(struct node));
third = (struct node *)malloc(sizeof(struct node));
head->data = 1; // setup first node
head->next = second; // note: pointer assignment rule
second->data = 2; // setup second node
second->next = third;
third->data = 3; // setup third link
third->next = NULL;
// At this point, the linked list referenced by "head"
// matches the list in the drawing.
return head;
}