Having trouble with T extractMin() method as I get a segfault error:

----------------- driver.cpp (Main File) -------------

#include  #include  #include "stackLL.h" #include "queueLL.h" #include "priorityQueueLL.h" using namespace std; int main() { /////////////Test code for stack /////////////// stackLL stk; stk.push(5); stk.push(13); stk.push(7); stk.push(3); stk.push(2); stk.push(11); cout << "Popping: " << stk.pop() << endl; cout << "Popping: " << stk.pop() << endl; stk.push(17); stk.push(19); stk.push(23); while( ! stk.empty() ) { cout << "Popping: " << stk.pop() << endl; } // output order: 11,2,23,19,17,3,7,13,5 stackLL stkx; stkx.push(5); stkx.push(10); stkx.push(15); stkx.push(20); stkx.push(25); stkx.push(30); stkx.insertAt(-100, 3); stkx.insertAt(-200, 7); stkx.insertAt(-300, 0); //output order: -300,30,25,20,-100,15,10,5,-200 while( ! stkx.empty() ) cout << "Popping: " << stkx.pop() << endl; /////////////////////////////////////// //////////Test code for queue /////////// queueLL Q; Q.enqueue(1); Q.enqueue(2); Q.enqueue(3); cout << "Dequeuing: " << Q.dequeue() << endl; //1 cout << "Dequeuing: " << Q.dequeue() << endl; //2 Q.enqueue(4); Q.enqueue(5); //3 4 5 while( ! Q.empty() ) { cout << "Dequeuing: " << Q.dequeue() << endl; } ///////////////////////////////////////// 

 //////////Test code for priority queue///// priorityQueueLL pQueue; const int SIZE = 20; //insert a bunch of random numbers for(int i=0; i pqs; pqs.insert("whale"); pqs.insert("snake"); pqs.insert("buffalo"); pqs.insert("elmo"); pqs.insert("fire"); pqs.insert("waffle"); //buffalo elmo fire snake waffle whale while( ! pqs.empty() ) { cout << pqs.extractMin() << endl; } /////////////////////////////////////////// //1) Template your queue class //2) Add a decimate method to your queue class queueLL qx; for(int i=1; i<=100; i++) qx.enqueue( i ); //Eliminate every 10th item from list //https://en.wikipedia.org/wiki/Decimation_(punishment) qx.decimate(); //1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 21 22... 98 99 while( ! qx.empty() ) cout << qx.dequeue() << endl; queueLL qy; qy.enqueue("sparticus"); qy.enqueue("maximus"); qy.enqueue("killicus"); qy.enqueue("awesomeicus"); qy.enqueue("gannicus"); qy.enqueue("varro"); qy.enqueue("oenomous"); qy.enqueue("slayicus"); qy.enqueue("bladeicus"); qy.enqueue("ted"); qy.enqueue("smashicus"); qy.enqueue("mallicus"); qy.enqueue("wussicus"); qy.enqueue("wimpicus"); qy.enqueue("crixus"); qy.decimate(); //Everyone but Ted. while( ! qy.empty() ) cout << qy.dequeue() << endl; return 0; }

-------------------- priorityQueueLL.h ------------------------

template  class priorityQueueLL { private: class node { public: //put what you need here.. } //add what you wish here public: priorityQueueLL() {} ~priorityQueueLL() {} //return true if empty, false if not bool empty() {} //add item void insert(T x) {} //remove and return smallest item T extractMin() {} };

--------------------- My T extractMin() method (Seg Fault Error) ---------------------------------------

//remove and return smallest item T extractMin() { // If list is empty if (head == nullptr) { // return default value of T return T(); }

// If not empty.... else { // Create a pointer to traverse the list node *current = head; node *previous = nullptr; node *minNode = head;

// Find the node with the minimum value while (current != nullptr) { if (current->data < minNode->data) { previous = current; minNode = current; }

current = current->next; }

// Remove the node with the minimum value if (minNode == head) { head = head->next; } else { previous->next = minNode->next; }

// Store the value of the minimum node T minValue = minNode->data;

// Delete the minimum node delete minNode;

// Return the minimum value return minValue; } }