c++ - Access Violation error when I debug my priority queue program -

i getting access violation error in code when try run it. program priority queue inserts value , prints heap after each insertion , min extract.

header file:

#pragma once /* header file priority queue class */ #ifndef priorityqueue_h #define priorityqueue_h  class priorityqueue { private:     int size;     int *data;  public:     static const int capacity = 50;     priorityqueue();//constructor     ~priorityqueue();//destructor     int getparent(int index);     int getleftchild(int index);     int getrightchild(int index);     void swap(int &, int &);     void insert(int item); //enqueue - heap_insert     void printarray(int []);     void heapify(int index);      //remove , return smallest item in priority queue     int extractmin();//dequeue      bool empty() const;     int min() const; //return smallest item }; #endif 

main code:

#include <iostream> #include "priorityqueue.h" using namespace std;     int main() {     priorityqueue myqueue; //class object      if (myqueue.empty())         cout << "my priority queue empty\n" << endl; //prompt      myqueue.insert(59); //insert value queue     cout << "after inserting 59 priority queue has" << endl;      myqueue.insert(41);     cout << "after inserting 41 priority queue has" << endl;      myqueue.insert(25);     cout << "after inserting 25 priority queue has" << endl;      myqueue.insert(12);     cout << "after inserting 12 priority queue has" << endl;      myqueue.insert(91);     cout << "after inserting 91 priority queue has" << endl;      myqueue.min();     myqueue.extractmin();     cout << "after extracting minimum value priority queue has" << endl;       myqueue.insert(34);     cout << "after inserting 34 priority queue has" << endl;      myqueue.insert(63);     cout << "after inserting 63 priority queue has" << endl;      myqueue.extractmin();     cout << "after extracting minimum value priority queue has" << endl;      myqueue.insert(75);     cout << "after inserting 75 priority queue has" << endl;      myqueue.insert(85);     cout << "after inserting 85 priority queue has" << endl;      myqueue.extractmin();     cout << "after extracting minimum value priority queue has" << endl;         cout <<"minimum value " ;      cout << myqueue.min() <<endl; //prints out heap min      system("pause");     return 0; } priorityqueue::priorityqueue() //constructor {     size = capacity;     &data[size]; }  priorityqueue::~priorityqueue() //destructor {  }  int priorityqueue::getparent(int index) //finds parent {     return (index - 1) / 2; }  int priorityqueue::getleftchild(int index) //finds left child {     return (2 * index) + 1; }  int priorityqueue::getrightchild(int index) //find right child {     return (2 * index) + 2; }  void priorityqueue::swap(int& item1, int& item2) //swaps value of 2 variables {      int temp = item1;     item1 = item2;     item2 = temp; }  void priorityqueue::heapify(int index) //heapifies heap {     int largest = index;     int l = getleftchild(index);     int r = getrightchild(index);      if (l < size && data[l] > data[index])     {         largest = l;     }      if (r < size && data[r] > data[largest])     {         largest = r;     }      if (largest != index)     {         swap(data[index], data[largest]);         heapify(data[size]);     }   }  void priorityqueue::printarray(int []) //prints array {     (int = 0; < capacity; i++)     {         cout << data[i] << ", ";     } }  int priorityqueue::extractmin() //finds min , removes {     int min = data[0];     data[0] = data[size - 1];     size - 1;     heapify(data[size]);     return min; }  int priorityqueue::min() const // finds min {     return data[0]; }  bool priorityqueue::empty() const // checks if heap empty {     if (data == null)     {         return true;     }     else     {         return false;     } }  void priorityqueue::insert(int item) //inserts values heap {     size += 1;     int = size - 1;     while (i > 0 && data[getparent(i)] < item)     {         data[i] = data[getparent(i)];         = getparent(i);     }     data[i] = item; } 

in constructor, &data[size]; nothing. need allocate memory it, possibly using new - data = new int[size] - or use smart pointer.