LINKED List BASICS

// AUTHOR : FUEANTA
// DATE : 31 OCT, 2016

#include "iostream"
using namespace std;

struct node {
    int number;
    node *next;
};

bool IsEmpty(node *);
int menu();
void insertAsFirstElement(node *&, node *&, int);
void insert(node *&, node *&, int);
void remove(node *&, node *&);
void showList(node *);

int main() {
    node *head = NULL;
    node *tail = NULL;
    int choice;
    int num;
    do {
        choice = menu();
        switch(choice) {
        case 1 :    cout << "Please enter a number: ";
                    cin >> num;
                    insert(head, tail, num);
                    break;
        case 2 :    remove(head, tail);
                    break;
        case 3 :    showList(head);
                    break;
        default:    cout << "\nChoose 4 to exit." << endl;
                    break;
        }

    } while (choice != '4');
    return 0;
}

bool IsEmpty(node *head) {
    if (head == NULL)
        return true;
    else return false;
}

int menu() {
    int choice;
    cout << "\n**MENU**\n" << endl;
    cout << "1. Insert an item." << endl;
    cout << "2. Delete an item." << endl;
    cout << "3. Show the list." << endl;
    cout << "4. Exit." << endl;
    cout << "\nCHOICE : ";
    cin >> choice; return choice;
}

void insertAsFirstElement(node *&head, node *&tail, int num) {
    node *temp = new node;
    temp->number = num;
    temp->next = NULL;
    head = temp;
    tail = temp;
}

void insert(node *&head, node *&tail, int num) {
    if (IsEmpty(head))
        insertAsFirstElement(head, tail, num);
    else {
        node *temp = new node;
        temp->number = num;
        temp->next = NULL;
        tail->next = temp;
        tail = temp;
    }
}

void remove(node *&head, node *&tail) {
    if (IsEmpty(head))
        cout << "\nThe list is already empty." << endl;
    else if (head == tail) {
        delete head;
        cout << "\nNode removed." << endl;
        head = tail = NULL;
    }
    else {
        node *temp = head;
        head = head->next;
        delete temp;
        cout << "\nNode removed." << endl;
    }
}

void showList(node *current) {
    if (IsEmpty(current))
        cout << "\nNothing to show. The list is empty." << endl;
    else {
        cout << "\nThe list contains : ";
        while (current != NULL) {
            cout << current->number << " ";
            current = current->next;
        }
    }
}