Thread: Binary Tree Heap Destructor failing

I get a runtime error when I add a destructor to my code.

Code:

#include <iostream>
#include <array>

using namespace std;

struct nodes {  int* elements; };

class heap
{
private:
    int length;
    nodes item;
    
public:
    heap();
    //~heap();
    void heap_size(int num);
    void push_heap(int item);
    void maxHeapify(int parent,int last);
    void print_heap();
};

heap::heap() { }

/*heap::~heap()
{
    delete [] item.elements;
}*/

//setting size of the array and making a new one
void heap::heap_size(int max)
{
    item.elements = new int [max];
}

//pushing numbers into the array
void heap::push_heap(int number)
{
    length++;
    item.elements[length-1] = number;
}

//sorting the array
void heap::maxHeapify(int parent, int last)
{
    int child = 2 * parent;
    while (child <= last)
    {
        if (child + 1 <= last && item.elements[child+1] > item.elements[child])
            child++;
        
        if (item.elements[child] > item.elements[parent])
        
            swap(item.elements[child], item.elements[parent]);
        
        parent = child;
        child = 2*parent;
        
    }

}

void heap::print_heap()
{
    
    for (int i=0; i<length; ++i)
    {
        cout<<"element["<<i<<"]"<<item.elements[i]<<",";
    }
}

int main(int argc, const char * argv[])
{
    
    
    cout<<"How many numbers do you want to enter into the heap?"<<endl;
    int amount;
    cin>>amount;
    
    heap myHeap;
    myHeap.heap_size(amount); //setting the size of the array
    
    int numbers=0;
    cout<<"Enter "<<amount<<" numbers into the heap and press enter to see the results printed."<<endl;
    
    for (int i=1; i<=amount; ++i)
    {
        cin>>numbers;
       myHeap.push_heap(numbers); //push numbers into the array
    }
    
    myHeap.maxHeapify(0, amount);
    
    myHeap.print_heap();
    
   // myHeap.~heap();
    
    
    return 0;
}

I get a runtime error when I add a destructor to my code.

Do you mean that you get a runtime error when you add the destructor code?

Or do you mean when you try to call the destructor?

Jim

Sorry...Runtime error

Again:

Do you mean that you get a runtime error when you add the destructor code?

Or do you mean when you try to call the destructor?

Please answer the above questions.

Also run the program through your debugger, the debugger should tell you exactly where it encounters the problem.

By the way you probably shouldn't be calling your destructor and you probably should have a check in your destructor insuring there are items that need to be deleted.

Jim

When I call my destructor it reads:

Binary Tree Heap(988,0x7fff784cd310) malloc: *** error for object 0x100000000: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
element[0]4,element[1]5,element[2]3,element[3]2,element[4]6

By the way you probably shouldn't be calling your destructor and you probably should have a check in your destructor insuring there are items that need to be deleted.

I thought if you have a pointer in a class or struct you need to free it when you are not using it anymore.

assert, never seen this before. I just read about it on cplusplus.com and from what I can gather is this used for debugging.
Why would a vector be better? Is it because with can use my vector.at(*it) or is there another reason?

Code:

struct nodes {  int* elements;};

class heap
{
private:
    int length;
    nodes item;
    
public:
    heap();
    heap(int);
    ~heap();
    void heap_size(int num);
    void push_heap(int item);
    void maxHeapify(int parent,int last);
    void print_heap();
};

heap::heap() { length = 0; item.elements=NULL; }

heap::heap(int l) :length(l) { }

heap::~heap()
{
    delete [] item.elements;
}

This runs, at least for me. I will not vouch for its correctness.
Again, though, you are better off using std::vector.

assert gave me a few issues not but I didn't use it in my functions just in the constructor like you. I forgot to add my code earlier.

Thank you everyone for the help. I can see why a vector is better.

Is there a library for this?

I have been reading about these and they are awesome.