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POLinkedList/Stack/Queue - Help with Dequeuing
 

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  1. POLinkedList/Stack/Queue - Help with Dequeuing
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    <p>I had to write a linked list, then turn it into a dynamic Stack, then turn that into a dynamic Queue. Well everything seems to work except the "dequeuing", right as the programs about to finish, it gives me an error: "An unhandled win32 exception occured in LinkedList_Stack_BNS11.exe [4972].". </p> <p>I'm only assuming it's the dequeuing, because as I step through and/or run the program, it runs smoothly up till that part, so maybe I sent one of the pointers wrong or something?</p> <p><strong>Output:</strong></p> <p>Enquing 5 items.... // Finsihes</p> <p>The values in the queue were (Dequeuing):</p> <p>0</p> <p>1</p> <p>2</p> <p>// Correct number in que but...</p> <p>//Program gives that error right here. When it should finish and close.</p> <p>If I included too much code let me know and I'll chop it down to just the "Dequeuing" (Which is in the very middle of all the stuff below)</p> <p>Thanks in advance for the help!! I'm just not seeing what I did wrong. Thinking it maybe has something to do with where "head" is pointing? Idk.</p> <p><strong>Header File:</strong></p> <pre><code>class NumberList { private: // struct ListNode { int value; // Value in this node struct ListNode *next; // Pointer to the next node }; ListNode *head; // List head pointer ListNode *rear; public: //Constructor NumberList() { head = NULL; rear = NULL; } //Destructor ~NumberList(); //Stack operations bool isEmpty(); //Queue operations void enqueue(int); void dequeue(int &amp;); }; #endif </code></pre> <p><strong>List_Stack_Queue.cpp:</strong></p> <pre><code>bool NumberList::isEmpty() { bool status; if(!head) status = true; else status = false; return status; } void NumberList::enqueue(int num) { ListNode *newNode; // Point to a new node // Allocate a new node and store num there. newNode = new ListNode; newNode-&gt;value = num; //If there are no nodes in the list // make newNode the first node. if(isEmpty()) { head = newNode; rear = head; //newNode-&gt;next = NULL; } else { rear-&gt;next = newNode; rear = rear-&gt;next; //newNode-&gt;next = head; //head = newNode; } } void NumberList::dequeue(int &amp;num) { ListNode *temp; if(isEmpty()) cout &lt;&lt; "The queue is empty.\n"; else { num = head-&gt;value; temp = head; head = head-&gt;next; delete temp; } } </code></pre> <p><strong>MAIN:</strong></p> <pre><code>const int MAX_VALUES = 3; // Create a DynIntQueue object. NumberList iQueue; // Enqueue a series of numbers. cout &lt;&lt; "Enqueuing " &lt;&lt; MAX_VALUES &lt;&lt; " items...\n"; for (int x = 0; x &lt; MAX_VALUES; x++) iQueue.enqueue(x); cout &lt;&lt; endl; //Dequeue and retrieve all numbers in the queue cout &lt;&lt; "The values in the queue were (Dequeuing):\n"; while(!iQueue.isEmpty()) { int value; iQueue.dequeue(value); cout &lt;&lt; value &lt;&lt; endl; } return 0; </code></pre>
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