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fixed null pointer reference #6

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26 changes: 18 additions & 8 deletions LinkedList.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@
// Default Constructor creates the head node.
LinkedList::LinkedList()
{

// Initialize the head node
cout << "\nEntering Constructor ..." << endl;
head = new node;
head -> song = "head (contains no song data)";
Expand All @@ -32,14 +34,20 @@ bool LinkedList::insertNode( node * newNode, int position )
cout << "Error: the given position is out of range." << endl;
return false;
}


// The first node after the head node.
// head->next is NULL.
if (!head -> next)
{
head -> next = newNode;
newNode->next = NULL;
listLength++;
cout << "Success: added '" << newNode -> song << "' to position " << position << ".\n";
cout << "Success: added'" << newNode -> song << "' to position " << position << ".\n";
cout << "listLength = " << listLength << endl;
return true;
}

int count = 0;
node * p = head;
node * q = head;
Expand All @@ -51,23 +59,26 @@ bool LinkedList::insertNode( node * newNode, int position )
newNode -> next = q;
listLength++;
cout << "Success: added '" << newNode -> song << "' to position " << position << ".\n";
cout << "listLength = " << listLength << endl;
cout << "listLength = = " << listLength << endl;
return true;
}
p = q;
q = p -> next;
count++;
}


// Insert at the last place of the list (the tail node.)
if (count == position)
{
p -> next = newNode;
newNode -> next = q;
newNode -> next = NULL;
listLength++;
cout << "Success: added '" << newNode -> song << "' to position " << position << ".\n";
cout << "listLength = " << listLength << endl;
cout << "Success: added boo'" << newNode -> song << "' to position " << position << ".\n";
cout << "listLength = = = " << listLength << endl;
return true;
}
cout << "Error: song node was not added to list." << endl;
// cout << "Error: song node was not added to list." << endl;
return false;
}

Expand Down Expand Up @@ -118,8 +129,7 @@ void LinkedList::printList()
int count = 0;
node * p = head;
node * q = head;
cout << "\n---------------------\n";
cout << " Song Playlist\n";

while (q)
{
p = q;
Expand Down
12 changes: 6 additions & 6 deletions LinkedList.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,17 +17,17 @@ 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
{

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.
//***********************************************************************************
// //***********************************************************************************
// // LinkedList is a list of singly-linked nodes.
// // In this project, it will represent a song playlist.
// //***********************************************************************************
class LinkedList
{
private:
Expand Down
22 changes: 15 additions & 7 deletions main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@
//***********************************************************************************

#include "LinkedList.h"
#include <cstring>
#include <iostream>
using namespace std;

int main()
Expand All @@ -19,7 +21,8 @@ int main()
node * B = new node;
B -> song = "I Stand Alone";
B -> artist = "Godsmack";



node * C = new node;
C -> song = "Heir Apparent";
C -> artist = "Opeth";
Expand All @@ -31,11 +34,16 @@ int main()
node * E = new node;
E -> song = "Blue Monday";
E -> artist = "New Order";

node * F = new node;
F -> song = "The Moth";
F -> artist = "Aimee Mann";


node * G = new node;
G -> song = "G String";
G -> artist = "Notre Dame";

// STEP 2: Build a list of three song nodes by appending to end of list.
LinkedList myList;
myList.insertNode(A, 1);
Expand All @@ -48,22 +56,22 @@ int main()
myList.insertNode(E, 2);
myList.printList();

// STEP 4: Insert node at the front of list.
// // STEP 4: Insert node at the front of list.
myList.insertNode(F,1);
myList.printList();

// STEP 5: Remove the last node from the list.
// // STEP 5: Remove the last node from the list.
myList.removeNode(6);
myList.printList();

// STEP 6: Remove the first node from the list.
// // 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.
// // STEP 7: Remove a node from the middle of the list.
myList.removeNode(3);
myList.printList();

cout<<"oi"<<endl;
return 0;
}