How to find the invalid pointer in a C++ tree program? - c++

Question

My program is simple, make a tree (min heap), and through a inorder traversal to store data to an array, then destroy the tree (heap).
When I run to the store step, the program crash. I can't find why, even I know the bug position (I comment some code and run to see whether it works and finally I find the bug position)
I think maybe I delete a invalid pointer, but I can't find where; please help me to find it.
When I input
6
1 2 3 4 5 6
it works
when I input
8
90 80 30 40 10 45 20 50
then crash.
I don't know what different between this two group numbers
#include <iostream>
typedef int ElementType;
struct BTree
{
ElementType data;
BTree *Left;
BTree *Right;
};
class BuildingMinHeap
{
ElementType *Elements;
int Size;
int Capacity;
BTree *root;
ElementType *inorder_array; // to store members inorderly
public:
BuildingMinHeap(int MaxSize, ElementType MinData): Size(0), Capacity(MaxSize+1)
{
Elements = new ElementType[MaxSize+1];
Elements[0] = MinData; // sentinel
root = NULL;
inorder_array = new ElementType[Size];
}
~BuildingMinHeap()
{
if (Elements)
delete [] Elements;
if (inorder_array)
delete [] inorder_array;
if (root != NULL)
DeleteBTree(root);
}
void Insert(ElementType item);
void genBTree(ElementType *a, int position); // call CreateBTree()
void ModifyArray(ElementType *input, int size); // call gen_inorder_array()
ElementType *getElements() {return Elements;}
BTree *getRoot() {return root;}
void DeleteBTree(BTree *root);
private:
BTree *CreateBTree(ElementType *a, int position);
void gen_inorder_array(const BTree *node);
};
void BuildingMinHeap::Insert(ElementType item)
{
int i;
i = ++Size;
for (; Elements[i/2] > item; i /= 2)
{
// Elements[0] is sentinel
Elements[i] = Elements[i/2];
}
Elements[i] = item;
}
BTree *BuildingMinHeap::CreateBTree(ElementType *a, int position) // array to Binary Tree list
{
BTree *new_node = new BTree;
if (position > Size)
return NULL;
new_node->data = a[position];
new_node->Left = CreateBTree(a, 2*position);
new_node->Right = CreateBTree(a, 2*position+1);
return new_node;
}
void BuildingMinHeap::genBTree(ElementType *a, int position) // call CreateBTree()
{
root = CreateBTree(a, position);
}
void BuildingMinHeap::DeleteBTree(BTree *root)
{
if (root == NULL)
return;
DeleteBTree(root->Left);
DeleteBTree(root->Right);
delete root;
root = NULL;
return;
}
void BuildingMinHeap::gen_inorder_array(const BTree *node) // to generate members of tree root inorderly
{
static int index = 0;
// like print inorder tree
if (node)
{
gen_inorder_array(node->Left);
inorder_array[index++] = node->data;
// std::cout << node->data << " ";
gen_inorder_array(node->Right);
}
}
void BuildingMinHeap::ModifyArray(int *input, int size) // call gen_inorder_array()
{
gen_inorder_array(root); // generate inorder_array, when I comment this line, it work
// below commented code is nothing about tree root member
//
// // generate<elements of inorder_array,elements' address of Elements> map
// std::map<int, int*> inorder_Ele_map;
// for (int i = 0; i != Size; i++)
// {
// ElementType *it = std::find(Elements+1, Elements+Size, *(inorder_array+i));
// inorder_Ele_map[*(inorder_array+i)] = Elements + (it-Elements);
// }
//
//
// // change Elements array according input array
// for (int i = 0; i != size; i++)
// {
// if (*(inorder_array+i) != *(input+i))
// {
// *(inorder_Ele_map[*(inorder_array+i)]) = *(input+i);
// }
// }
}
int main(void)
{
int n;
std::cin >> n;
int *input = new int[n];
for (int i = 0; i != n; i++)
std::cin >> input[i];
BuildingMinHeap h(n, -999); // empty heap;
for (int i = 0; i != n; i++)
h.Insert(input[i]); // insert element to heap
h.genBTree(h.getElements(), 1); // generate Binary Tree(pointer) from Elements array, index 1 begin
// so far it work
h.ModifyArray(input, n); // if I comment this line, it would work
h.DeleteBTree(h.getRoot()); // I have already do call this function in destructor,
// but in destructor I call it when root != NULL,
// I have no idea when I comment this line, there are a crash.
delete [] input;
return 0;
}