linkedlist_dynamic.c

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>

typedef struct node  // define our own custom struct for each node in the linked list
{
    int number;
    struct node *next;
}
node;

node* create_node(int);  // create node handles the malloc line, checking if it's not null and returns the completed node
void add_node(node *list, node *n);  // And add node loops through the list until it reaches the end and adds the new node to that point
void print_list(node *list);
void free_memory(node *list);

int main(void)
{
    int input = get_int("Please enter how many nodes you would like to create in the linked list? \n");
    node *list = NULL;  // create the list pointer variable, that will anticipate to be pointed to something of a "node" datatype, initalize it to NULL asits not pointing to anything

    node *n = malloc(sizeof(node));  // malloc() "node 2" in our memory + point out *n pointer to this node
    if (n != NULL)  // saftey check to ensure n is not pointing to a NULL value in our memory
    {
        n->number = 0;  // set the number field of the node our "*n" is currently pointing to: 2
        n->next = NULL;   // set the next field of the node our "*n" is currently pointing to: NULL
    }
    list = n; // point our "*list" pointer to the same node our "*n" pointer is pointing to (at the start of this program list will be pointing to the head of the linked list)

    for (int i = 1; i < input; i++) // start counting i at 1 since we declared the first node as "0"
    {
        n = create_node(i);  // use creat_node to create a new node + also take the pointer to a node this function returns + assign it back to n
        add_node(list, n);
    }

    print_list(list);
    free_memory(list);
    return 0;
}

node* create_node(int i)  // our function to generate a node with the number we got from "i' in main()" "node 0", then "node 1" , then "node 2" etc
{
    node *n = malloc(sizeof(node)); // a new n pointer that will malloc "node i" in memory + point our "*n" pointer to this node
    if (n != NULL)  // saftey check to ensure n is not pointing to a NULL value in our memory
    {
        n->number = i;  // set the number field of the node our "*n_2" is currently pointing to: whatever "i" is (this draws a line in our linked list)
        n->next = NULL;  // set the next field of the node our "*n" is currently pointing to: NULL
    }
    return n;
}

void add_node(node *list, node *n)  // takes in paramaters for the 1. "list" pointer (that is anticipating to point to a node) and the "n" pointer (to point to the "n" node itself)
{
    node *tmp = list; // create a temp pointer, that will anticipate to be poiinted to something of a "node" datatype, and point it to where *tmp is pointing to, drawing a link
    while (tmp->next != NULL) // every time when looping through the linked list, if the current node tmp is  sitting on isn't NULL
    {
        tmp = tmp->next; // then migrate the temp pointer to the next node in the linked list
    }
    tmp->next = n; // then, set tmp->next field in this current node to = n, to point to where *n is pointing to, drawing another link between the temp node and node n after it.
}

void print_list(node *list) // takes in paramater for the list pointer (that is anticipating to point to a node)
{
    printf("Numbers in linked list:\n");
    node *tmp = list; // make a temp pointer that will point to the head of the linked list

    if (list == NULL)  // if the list pointer variable pointing to the head of thelinked list is NULL
    {
        printf("The linked list is empty\n");
    }
    else
    {
        while (tmp != NULL)  // keep performing this while loop until temp is not longer pointing to a node after in the linked list
        {
            printf("%d\n", tmp->number);  // print out the current nodes.number where tmp is pointing to
            tmp = tmp->next;  // then after this, update temp to point to the next node in the linked list to perform this action again
        }
    }
}

void free_memory(node *list)
{
    node* tmp = list;

    while (list != NULL)
    {
        tmp = list;
        list = list->next;
        free(tmp);
    }
}