c++ visual studio 2019

Do not use #include

(saw another method where they used bool List::empty() const and void List::print() but it does not work)

(cannot change list2.h when making it a circular list and cannot change class node)

(can change list2.h after making it a circular list)

1. Convert it to a circular list. The node after the last node should be the first node. The node before the first node should be the last node. Do not change the implementation of class Node.
   1. Implement all operations currently available in the class List. Do not change file list2.h.
   2. Add a method empty(), which should return true if the circular list is empty and false otherwise.
   3. Add a method print() to print the values in the nodes of the circular list, from the first to the last node.

list2.h---------------------------------------------------------------------------------------------------------------------------

#include #include #include

using namespace std;

class List; class Iterator;

class Node { public: /** Constructs a node with a given data value. @param s the data to store in this node */ Node(string s); private: string data; Node* previous; Node* next; friend class List; friend class Iterator; };

class List { public: /** Constructs an empty list; */ List(); /** Appends an element to the list. @param data the value to append */ void push_back(string data); /** Inserts an element into the list. @param iter the position before which to insert @param s the value to append */ void insert(Iterator iter, string s); /** Removes an element from the list. @param iter the position to remove @return an iterator pointing to the element after the erased element */ Iterator erase(Iterator iter); /** Gets the beginning position of the list. @return an iterator pointing to the beginning of the list */ Iterator begin(); /** Gets the past-the-end position of the list. @return an iterator pointing past the end of the list */ Iterator end(); private: Node* first; Node* last; friend class Iterator; };

class Iterator { public: /** Constructs an iterator that does not point into any list. */ Iterator(); /** Looks up the value at a position. @return the value of the node to which the iterator points */ string get() const; /** Advances the iterator to the next node. */ void next(); /** Moves the iterator to the previous node. */ void previous(); /** Compares two iterators @param b the iterator to compare with this iterator @return true if this iterator and b are equal */ bool equals(Iterator b) const; private: Node* position; List* container; friend class List; };

List2 cpp---------------------------------------------------------------------------------------------------

#include #include #include #include #include #include #include "list2.h"

using namespace std;

Node::Node(string s) { data = s; previous = NULL; next = NULL; }

List::List() { first = NULL; last = NULL; }

void List::push_back(string data) { Node* new_node = new Node(data); if (last == NULL) { first = new_node; last = new_node; } else { new_node->previous = last; last->next = new_node; last = new_node;

} last->next = first; first->previous = last; }

void List::insert(Iterator iter, string s) { if (iter.position == NULL) { push_back(s); return; } Node* new_node = new Node(s); Node* after = iter.position; Node* before = after->previous;

new_node->previous = before; new_node->next = after; if (before == last) { first = new_node; first->previous = last; last->next = first; } else { before->next = new_node; }

}

Iterator List::erase(Iterator iter) { assert(iter.position != NULL); Node* remove = iter.position; Node* before = remove->previous; Node* after = remove->next;

if (remove == first) { if (first == last) { first = NULL; last = NULL; } else { first = after; first->previous = last; last->next = first; } } else before->next = after;

if (remove == last) { if (first != last) { last = before; first->previous = last; last->next = first; } } else { after->previous = before; }

delete remove;

Iterator r; r.position = after; r.container = this; return r; }

Iterator List::begin() { Iterator iter; iter.position = first; iter.container = this; return iter; }

Iterator List::end() { Iterator iter; iter.position = last; iter.container = this; return iter; }

Iterator::Iterator() { position = NULL; container = NULL; }

string Iterator::get() const { assert(position != NULL); return position->data; }

void Iterator::next() { assert(position != NULL); position = position->next; }

void Iterator::previous() { assert(position != container->first); if (position == NULL) position = container->last; else position = position->previous; }

bool Iterator::equals(Iterator b) const { return position == b.position; }

int main() { List staff;

staff.push_back("Tom"); staff.push_back("Dick"); staff.push_back("Harry"); staff.push_back("Juliet");

Iterator pos; pos = staff.begin(); pos.next(); pos.next(); pos.next();

staff.insert(pos, "Romeo");

pos = staff.begin(); pos.next();

staff.erase(pos);

for (pos = staff.begin(); !pos.equals(staff.end()); pos.next()) cout << pos.get() << " ";

list mylist{ "Tom", "Dick", "Harry", "Juliet", "Romeo" }; if (mylist.empty()) cout << "true"; else cout << "false";

return 0; }