C++ Stack using a doubly linked list - c++

Question

I'm trying to implement a stack using a doubly linked list. I know that the functions for my stack class (push, pop) should contain calls to member functions of my doubly linked list class, but I'm having trouble actually implementing that.
dlist.cpp:
#include <iostream>
#include <fstream>
#include <string>
#include "dlist.hpp"
using namespace std;
void dlist::appendNodeFront(int shares, float pps){
Node *n = new Node(shares, pps);
if(front == NULL){
front = n;
back = n;
}
else {
front->prev = n;
n->next = front;
front = n;
}
}
void dlist::appendNodeBack(int shares, float pps){
Node *n = new Node(shares, pps);
if(back == NULL){
front = n;
back = n;
}
else {
back->next = n;
n->prev = back;
back = n;
}
}
void dlist::display(){
Node *temp = front;
cout << "List contents: ";
while(temp != NULL){
cout << temp->value << " ";
temp = temp->next;
}
cout << endl;
}
void dlist::display_reverse(){
Node *temp = back;
cout << "List contents in reverse: ";
while(temp != NULL){
cout << temp->value << " ";
temp = temp->prev;
}
cout << endl;
}
void dlist::destroyList(){
Node *T = back;
while(T != NULL){
Node *T2 = T;
T = T->prev;
delete T2;
}
front = NULL;
back = NULL;
}
stack.cpp:
#include <iostream>
#include <fstream>
#include <string>
#include "stack.hpp"
using namespace std;
stack::stack(){
int i;
for(i = 0; i < 1500; i++){
shares[i] = 0;
pps[i] = 0;
}
first = 0;
}
void stack::push(int num, float price){
if(first ==(1500-1)){
cout << "Stack is full" << endl;
return;
}
first++;
shares[first] = num;
pps[first] = price;
return;
}
void stack::pop(int *num, float *price){
if(first == -1){
cout << "Stack is empty" << endl;
return;
}
num = &shares[first];
price = &pps[first];
cout << shares[first] << endl;
cout << pps[first] << endl;
shares[first] = 0;
pps[first] = 0;
first--;
return;
}
Should the push function in stack basically be a call to appendNodeFront() or appendNodeback()? Any help or advice is greatly appreciated!

Answer 1

You can create a stack class, then use linked list class as its container. In a linked list class there is virtually no limit to the number of items, so you add artificial limit to make it work like a stack. In a linked list, items can be added/removed anywhere in the list, you can limit add/remove the tail node only to make it work like stack. The example below demonstrate the usage.
Node that this is purely a programming exercise. Stack is relatively primitive compared to Doubly-linked list. Encapsulating a linked-list inside stack has no advantage. Also note, I declared all members as public for the sake of simplifying the problem, you may want to change some members to protected/private
#include <iostream>
#include <fstream>
#include <string>
using std::cout;
class Node
{
public:
Node *prev;
Node *next;
int shares;
float pps;
Node(int vshares, float vpps)
{
shares = vshares;
pps = vpps;
prev = next = nullptr;
}
};
class dlist
{
public:
Node *head;
Node *tail;
dlist()
{
head = tail = nullptr;
}
~dlist()
{
destroy();
}
void push_back(int shares, float pps)
{
Node *node = new Node(shares, pps);
if (head == NULL)
{
head = tail = node;
}
else
{
tail->next = node;
node->prev = tail;
tail = node;
}
}
void destroy()
{
Node *walk = head;
while (walk)
{
Node *node = walk;
walk = walk->next;
delete node;
}
head = tail = nullptr;
}
};
class stack
{
public:
int maxsize;
int count;
dlist list;
stack(int size)
{
count = 0;
maxsize = size;
}
void push(int num, float price)
{
if (count < maxsize)
{
list.push_back(num, price);
count++;
}
}
void pop()
{
Node *tail = list.tail;
if (!tail)
{
//already empty
return;
}
if (tail == list.head)
{
//only one element in the list
delete tail;
list.head = list.tail = nullptr;
count--;
}
else
{
Node *temp = list.tail->prev;
delete list.tail;
list.tail = temp;
list.tail->next = nullptr;
count--;
}
}
void display()
{
Node *walk = list.head;
while (walk)
{
cout << "(" << walk->shares << "," << walk->pps << ") ";
walk = walk->next;
}
cout << "\n";
}
};
int main()
{
stack s(3);
s.push(101, 0.25f);
s.push(102, 0.25f);
s.push(103, 0.25f);
s.push(104, 0.25f);
s.display();
s.pop();
s.display();
return 0;
}