Linked List - Iterative

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

typedef struct Node {
    int key;
    struct Node *next;
} Node;

Node *create_node(int key, Node *next=nullptr) {
    Node *ptr = (Node*)malloc(sizeof(Node));
    ptr->key = key;
    ptr->next = next;
    return ptr;
}

Node *push_front(Node *head, int key) {
    return create_node(key, head);
}

Node *push_back(Node *head, int key) {
    if (!head)
        return create_node(key);
    Node *curr = head;
    while (curr->next)
        curr = curr->next;
    curr->next = create_node(key);
    return head;
}

Node *insert_in_order(Node *head, int key) {
    if (!head)
        return create_node(key);
    Node *curr = head;
    while (curr->next && curr->next->key < key)
        curr = curr->next;
    curr->next = create_node(key, curr->next);
    return head;
}

Node *find_key(Node *head, int key) {
    Node *curr = head;
    while (curr) {
        if (curr->key == key)
            return curr;
        curr = curr->next;
    }
    return nullptr;
}

Node *delete_key(Node *head, int key) {
    if (!head)
        return nullptr;
    if (head->key == key) {
        Node *tmp = head->next;
        free(head);
        return tmp;
    } else {
        Node *curr = head;
        while (curr->next && curr->next->key != key)
            curr = curr->next;
        if (curr->next && curr->next->key == key) {
            Node *tmp = curr->next->next;
            free(curr->next);
            curr->next = tmp;
        }
        return head;
    }
}

void print_list(Node *head) {
    Node *curr = head;
    while (curr) {
        printf("%d -> ", curr->key);
        curr = curr->next;
    }
    printf("NULL\n");
}

Node *free_list(Node *head) {
    Node *curr = head;
    while (curr) {
        Node *tmp = curr->next;
        free(curr);
        curr = tmp;
    }
    return nullptr;
}

int main()
{
    Node *p = nullptr, *head = nullptr;
    head = insert_in_order(head, 10);
    head = insert_in_order(head, 20);
    head = insert_in_order(head, 30);
    print_list(head);
    p = find_key(head, 50);
    print_list(p);
    p = find_key(head, 30);
    print_list(p);
    p = find_key(head, 20);
    print_list(p);
    head = delete_key(head,50);
    head = delete_key(head,20);
    print_list(head);
    head = free_list(head);
    print_list(head);

    return 0;
}