//This program introduced the linked list data structure
//We are able to insert at the end of a linked list with 
//create_node function and are able to traverse the list
//with the print function

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

//Define a node 
struct node {
    int data;
    struct node *next;
};

//Helper functions
//TODO: Fill in the output and inputs to complete prototypes
struct node *create_node(int data, struct node *next);
void print_list(struct node *head);

int main (void) {
    //TODO: Create a pointer to the first node of the list, and the first node
    //The first node is pointing to NULL as the next node, since there 
    //are no other nodes
    struct node *head = create_node(4, NULL);
    
    //TODO: Create the next node, with data 2 and pointing next to the current head
    //Therefore you are making this new node the head of the list
    head = create_node(2, head);
    
    //TODO: Create the next node, with data 1 and pointing next to the current head
    //Therefore you are making this new node the head of the list
    head = create_node(1, head);
    
    //TODO: What are we giving our print_list function?
    print_list(head);
    
    return 0;
}

//Function that creates a node
// TODO: Fill in input and output to complete function
struct node *create_node(int data, struct node *next) {
    //TODO: create a pointer to a node of type struct node 
    //by using malloc to allocate memory
    
    //(4, NULL)
    // new_node = some address that points to that node
    //(2, head) 
    struct node *new_node = malloc(sizeof(struct node)); 
    
    //TODO: Initialise the data by setting it to the given int
    //new_node (int data) = 4
    //new_node (int data) = 2
    new_node->data = data;
    
    //TODO: Initialise next pointer to point to the next node given
    //new_node (struct node *next) = NULL
    // new_node(struct node *next) = head (4) 
    new_node->next = next;
    
    //TODO: What will I need to return?
    return new_node;
}

//Function that prints a list
// TODO: Fill in input and output to complete function
void print_list(struct node *head) {
//TODO: create a way to keep track of where we are in the list
    struct node *current = head;
//TODO: What will be the condition where our while loop can stop
    while (current != NULL) {
        //TODO: print out the node value
        printf("%d -> ", current->data);
        //TODO: increment to the next node
        current = current->next;
    }
    //Finish printing list with an X
    printf("X\n");
}