This is a program of a singly linked list of songs and artists, but now I have to make it into a double linked list that points forward to the next node and pointing back to the previous node. able to move forward and backward through the lis, accomodate this into my program below.

=======================================================================================LinkedList.h #ifndef LinkedList_h #define LinkedList_h

#include #include using namespace std;

//******************************************************************* // Node structs contain data and a pointer to the next node. // In this project, it will represent a song/artist combination. //******************************************************************* struct node { string song; string artist; node * next; };

//******************************************************************* // LinkedList is a list of singly-linked nodes. // In this project, it will represent a song playlist. //******************************************************************* class LinkedList { private: // Head of the list contains no song data, // but points to the song playlist. node * head; int listLength; public: // Default Constructor creates the head node. LinkedList(); // Setter adds a node to the list at a given position. // Takes a node and list position as parameters. // Position must be between 1 and the number of data nodes. // Returns true if the operation is successful. bool insertNode( node * newNode, int position ); // Setter removes a node by its given position. // Returns true if the operation is successful. bool removeNode( int position );

// Prints each node in the list in consecutive order, // starting at the head and ending at the tail. // Prints list data to the console. void printList(); // Destructor de-allocates memory used by the list. ~LinkedList(); };

#endif ================================================================================================== LinkedList.cpp #include "LinkedList.h"

// Default Constructor creates the head node. LinkedList::LinkedList() { head -> song = "head (contains no song data)"; head -> artist = "head (contains no artist data)"; head -> next = NULL; listLength = 0; }

// Setter adds a node to the list at a given position. // Takes a node and list position as parameters. // Position must be between 1 and the number of data nodes. // Returns true if the operation is successful. bool LinkedList::insertNode( node * newNode, int position ) { if ((position <= 0) || (position > listLength + 1)) { cout << "nError: the given position is out of range.n"; return false; } if (head -> next == NULL) { head -> next = newNode; listLength++; return true; } int count = 0; node * p = head; node * q = head; while (q) { if (count == position) { p -> next = newNode; newNode -> next = q; length++; return true; } p = q; q = p -> next; count++; } if (count == position) { p -> next = newNode; newNode -> next = q; listLength++; return true; } cout << "nError: node was not added to list.n"; return false; }

// Setter removes a node by its given position. // Returns true if the operation is successful. bool LinkedList::removeNode( int position ) { if ((position <= 0) || (position > listLength + 1)) { cout << "nError: the given position is out of range.n"; return false; } if (head -> next == NULL) { cout << "nError: there is nothing to remove.n"; return false; } int count = 0; node * p = head; node * q = head; while (q) { if (count == position) { p -> next = q -> next; delete q; listLength--; return true; } p = q; q = p -> next; count++; } cout << "nError: nothing was removed from the list.n"; return false; }

// Prints each node in the list in consecutive order, // starting at the head and ending at the tail. // Prints the data to the console. void LinkedList::printList() { node * p = head; node * q = head; cout << "n---------------------------n"; cout << "Song Playlist n"; while (q) { p = q; cout << "n-----------------------------n"; cout << "t position: " << count << endl; cout << "t song: " << p -> song << endl; cout << "t artist: " << p -> artist << endl; q = p -> next; count++; } }

// Destructor de-allocates memory used by the list. LinkedList::~LinkedList() { node * p = head; node * q = head; while (q) { p = q; q = p -> next; if (q) delete p; } } ======================================================================================= main.cpp #include "LinkedList.h" using namespace std;

int main() { // STEP 1: Create some unlinked song nodes. node * A = new node; A -> song = "We Are"; A -> artist = "Vertical Horizon"; node * B = new node; B -> song = "I Stand Alone"; B -> artist = "Godsmack"; node * C = new node; C -> song = "Heir Apparent"; C -> artist = "Opeth"; node * D = new node; D -> song = "Fear of the Dark"; D -> artist = "Iron Maiden"; node * E = new node; E -> song = "Blue Monday"; E -> artist = "New Order"; node * F = new node; F -> song = "The Moth"; F -> artist = "Aimee Mann"; // STEP 2: Build a list of three song nodes by appending to end of list. LinkedList myList; myList.insertNode(A, 1); myList.insertNode(B, 2); myList.insertNode(C, 3); myList.insertNode(D, 4); myList.printList(); // STEP 3: Insert a node into middle of list. myList.insertNode(E, 2); myList.printList(); // STEP 4: Insert node at the front of list. myList.insertNode(F,1); myList.printList(); // STEP 5: Remove the last node from the list. myList.removeNode(6); myList.printList(); // STEP 6: Remove the first node from the list. myList.removeNode(1); myList.printList(); // STEP 7: Remove a node from the middle of the list. myList.removeNode(3); myList.printList(); return 0; }