Question & Answer: Makefile app.cpp st.cpp list.h The LinkedList class is specified in list.h. Write the code in the file list.cpp to implem…..

#include “list.h”

LinkedList::LinkedList(){
head = NULL;
tail = NULL;
}

bool LinkedList::add(int val){
Node *temp,*ptr;
temp = new Node;
temp->data = val;

if (head == NULL){
head = temp;
tail = temp;
temp->next = NULL;
temp->prev = NULL;
}
else {
temp->prev = tail;
tail->next = temp;
temp->next = NULL;
tail = temp;
}
return true;
}

bool LinkedList::remove(int val){
Node *curr;
curr = head;
bool result = false;
if (curr->data == val){
if (head->next == NULL){
head = NULL;
tail = NULL;
}
else {
head = head->next;
head->prev = NULL;
}
return true;
}
while (curr->next != NULL && curr->next->data != val)
curr = curr->next;
if (curr->next != NULL){
if (tail == curr->next)
tail = curr;
result = true;
curr->next = curr->next->next;
if (curr->next != NULL){
curr->next->prev = curr;
}
}
return result;
}

void LinkedList::printAscending() const {
Node *curr;
curr = head;
while (curr !=NULL){
cout << curr->data << ” “;
curr = curr->next;
}
cout << endl;

}

void LinkedList::printDescending() const {
Node *curr;
curr = tail;
while (curr !=NULL){
cout << curr->data << ” “;
curr = curr->prev;
}
cout << endl;
}