Question

Write the following method definitions for the DLL class:

(5 pt) void push(string t, string a, int m, int s);

This pushes a new node onto the end of the list. If there are no nodes in the list, it creates the first node and adds it. Otherwise it places a new node onto the end of the list. t is the song’s title,a is the song’s artist, m is the number of minutes the song runs for, and s is the number of seconds the song runs for

For testing:  When my readList method in Playlist.hpp is called, it continuously calls the list’s push method. So if this method reads in the list, and then print it out successfully, that is sufficient for testing. Although for your purposes, it will be notably easier to test once you’ve written printList() (explained below).

(6 pt) void printList();

This method should print out the list. Note that I have included a method for printing out each song object in the song class definitions, called printSong(). If you call that, the songs will printed out in the format you see in the output

For testing: after every action you take, printList is called from the Playlist method definitions. Thus this will be tested automatically as we (and you) run the code.

#include "DNode. hpp" #include "DLL. hpp" #include <iostream> #include <stdlib.h> using namespace std; DLL::DLL({ // constructor initializes an empty list last = NULL; first = NULL; numSongs = 0; } DLL::DLL (string t, string 1, int n, int s){ // constructor, initializes a list with one new node with data x DNode in new DNode (tal.mes) first = n; last = n; numSongs=1; }

Answer 1

void DLL::push(string t, string a, int m, int s){
   DNode *n = new DNode(t,a,m,s);
  
   if(first == NULL){
       first = n;
       last = n;
   }
  
   else{
       n->setPrev(last);
       last->setNext(n);
       last = n;
   }
  
   numSongs++;
}

void DLL:: printList(){
   DNode* current = first;
  
   while(current != NULL){
       current->printSong();
       current = current->getNext();
   }
}