Linkedlist and arraylist speed comparison in c++ - c++

Question

I have to make two types of list data types for my data structures class, an ArrayList and a Linkedlist. The ArrayList will be based on arrays and the LinkedList will be based on nodes, then i need to compare their performance on adding (on the desired position), updating and removing elements from front, end and middle of the list for lists with 100,1000 and 10000 elements. The point of the homework is to show that linked lists are faster. I made both structures and all the functions but when i test them the result always shows that my array lists are faster. Can someone please tell me why my linked lists works slower?
struct ArrayList {
int* head;
int size;
void build();
void add(int, int);
void update(int, int);
void remove(int);
void print();
void clear();
};
struct Node {
int data;
Node* next;
};
struct LinkedList {
Node* head;
int size;
void build();
void add(int, int);
void update(int, int);
void remove(int);
void print();
void clear();
};
void LinkedList::build() {
head = NULL;
size = 0;
}
void LinkedList::add(int index, int value) {
Node* n = new Node();
n->data = value;
if (head == NULL) { // adding to an empty list
head = n;
size++;
}
else {
if (index == 0) { // adding at front
n->next = head;
head = n;
size++;
}
else if (index < size) { // adding inside
Node* p = head;
int c = 1;
while (c < index) {
p = p->next;
c++;
}
n->next = p->next;
p->next = n;
size++;
}
else if (index == size) { // adding at the end
Node* p = head;
while (p->next) {
p = p->next;
}
p->next = n;
size++;
}
else {
cout << "index out of range";
}
}
}
void ArrayList::build() {
size = 0;
head = new int[size];
}
void ArrayList::add(int index, int value) {
int* arr = new int[size + 1];
if (index == size) { //adding at the end
for (int i = 0; i < size; i++) {
arr[i] = head[i];
}
arr[size] = value;
delete head;
head = arr;
size++;
}
else if (index < size) { //adding inside or front
for (int i = 0; i < index; i++) {
arr[i] = head[i];
}
arr[index] = value;
for (int i = index; i < size; i++) {
arr[i + 1] = head[i];
}
delete head;
head = arr;
size++;
}
else {
cout << "index out of range.";
}
}
Testing code
ArrayList* a = new ArrayList();
LinkedList* l = new LinkedList();
l->build();
a->build();
int n = 10000;
for (int i = 0; i < n; i++) {
l->add(i, i);
a->add(i, i);
}
auto begin = std::chrono::high_resolution_clock::now();
a->add(n, 1);
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
auto begin2 = std::chrono::high_resolution_clock::now();
l->add(n, 1);
auto end2 = std::chrono::high_resolution_clock::now();
auto elapsed2 = std::chrono::duration_cast<std::chrono::nanoseconds>(end2 - begin2);
cout << "with " << n << " " << "elements" << endl;
cout << endl;
cout << "ArrayList adding time: " << elapsed.count() << " nano-seconds" << endl;
cout << endl;
cout << "LinkedList adding time: " << elapsed2.count() << " nano-seconds" << endl;