Linked List 1

#include <stdio.h>
#include <stdlib.h> // for malloc(), free()

typedef struct Node {
    int data;
    struct Node *next;
} Node_t;

typedef int bool_t;

//  TODO:
/// Handle case exceptions when HEAD is empty in pop(), push()
//  Add boolean isEmpty()
//  Add function: clear() which clears the linked list (leaves nothing, and cleans up memory)
//  Add function: length() which returns how many element does the list possess
//  Add function: addMany(@param array) which adds elements of the array (or another linked list)
//  ...

bool_t isEmpty(Node_t *node) {
    return node == NULL;
}

Node_t *createNode(int data, Node_t *next_node) {
    Node_t *node = (Node_t *)malloc(sizeof(Node_t));;
    node->data = data;
    node->next = next_node;
}

void push(Node_t *head, int data) {
    Node_t *new_node = createNode(data, NULL);
    Node_t *it = head;
    while (it->next != NULL) {
        it = it->next;
    }
    it->next = new_node;
}

void printList(Node_t *head) {
    Node_t *it = head;
    while (!isEmpty(it)) {
        printf("%d->", it->data);
        it = it->next;
    }
    printf("\n");
}

int pop(Node_t *head) {
    int ret;

    // Handle case if HEAD has only 1 element
    if (head->next == NULL) {
        ret = head->data;
        free(head);
        return ret;
    }

    Node_t *it = head;
    while (it->next->next != NULL) {
        it = it->next;
    }
    ret = it->next->data;
    free(it->next);
    it->next = NULL;
    return ret;
}

int main(void) {
    Node_t *HEAD = createNode(10, NULL);
    push(HEAD, 20);
    push(HEAD, 3);
    printList(HEAD);
    // prints: 10->20->3

    pop(HEAD); // pops 3
    printList(HEAD); // prints: 10->20

    return 0;
}