Soal UTS

#include <iostream>
using namespace std;

struct Node{
    int data;
    Node *next;
    Node *prev;
};

Node *n=NULL, *head=NULL, *tail=NULL, *x=NULL;

void buatNodeBaru(int i){
    n = new Node;
    n->data = i;
    n->prev = NULL;
    head = n;
    tail = n;
    tail->next = NULL;
}

void tambahDiBelakang(int i){
    n = new Node;
    n->data = i;
    n->prev = tail;
    tail->next = n;
    tail = n;
    tail->next = NULL;
}

void tambahDiDepan(int i){
    n = new Node;
    n->data = i;
    n->next = head;
    head->prev = n;
    n->prev = NULL;
    head = n;
}

void tambahDiTengah(int i, int j){
    x = head;
    while(x->data != j) x=x->next;
    n = new Node;
    n->data = i;
    n->next = x->next;
    x->next = n;
    n->prev = x;
    x = n->next;
    x->prev = n;
}

void tambahData(int i){
    if (head==NULL)
        buatNodeBaru(i);
    else
        tambahDiBelakang(i);
}

void hapusDiDepan(){
    x = head;
    head = x->next;
    head->prev = NULL;
    delete(x);
    x = NULL;
}

void hapusDiBelakang(){
    x = tail;
    tail = tail->prev;
    tail->next = NULL;
    delete(x);
    x = NULL;
}

void hapusDiTengah(int i){
    n = NULL;
    x = head;
    while(x->data != i){
        n = x;
        x = x->next;
    }
    n->next = x->next;
    x = x->next;
    delete(x->prev);
    x->prev = n;

}

void tampilDariDepan(){
    x = head;
    while(x != NULL){
        cout << x->data << " ";
        x = x->next;
    }
}

void tampilDariBelakang(){
    x = tail;
    while(x != NULL){
        cout << x->data << " ";
        x = x->prev;
    }
}

bool cariData(int i){
    x = head;
    while(x != NULL){
        if (i == x->data) return true;
        x = x->next;
    }
    return false;
}

void hapusData(int i){
    if (!cariData(i) || head == NULL) return;

    if (i == head->data)
        hapusDiDepan();
    else if (i == tail->data)
        hapusDiBelakang();
    else
        hapusDiTengah(i);
}

int getJmlNode(){
    // lengkapi isi method ini
    // method berfungsi untuk mengembalikan nilai
    // berupa jumlah node yg terdapat dalam list
}

int main(){
    tambahData(10);
    tambahData(20);
    tambahData(30);
    tambahData(40);
    tambahData(50);
    tambahData(60);

    cout << "Jumlah node: " << getJmlNode() << endl; //output ->  Jumlah node: 6
}