How to balance a Binary Search Tree? - c++

Question

I'm practicing binary tree problems on LeetCode and I'm struggling at the moment with balancing a binary search tree. I feel as if I got the logic of it, but I'm getting weird errors when using pointers.
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
void inOrder(TreeNode* root, vector<int> bst)
{
if (root != NULL)
{
inOrder(root->left, bst);
bst.push_back(root->val);
inOrder(root->right, bst);
}
}
TreeNode* Insert(TreeNode* bt, int median)
{
if (bt == NULL)
{
return new TreeNode(median);
}
if (median > bt->val)
{
bt->right = Insert(bt->right, median);
}
else
{
bt->left = Insert(bt->left, median);
}
return bt;
}
TreeNode* balanceBST(TreeNode* root) {
vector<int> sortedBST;
inOrder(root, sortedBST);
int size = sortedBST.size();
TreeNode* balancedBST;
int mid;
while (size != 0)
{
if (size % 2 == 1 || size % 2 == 0)
mid = size/2;
if (balancedBST == NULL)
{
balancedBST = new TreeNode(sortedBST[mid]);
}
else
{
TreeNode* node = Insert(balancedBST, sortedBST[mid]);
}
sortedBST.erase(sortedBST.begin() + mid);
--size;
}
return balancedBST;
}
};
The error I received was this:
=================================================================
==30==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffc15eb8028 at pc 0x000000374488 bp 0x7ffc15eb7dd0 sp
0x7ffc15eb7dc8 READ of size 8 at 0x7ffc15eb8028 thread T0
#5 0x7fac728370b2 (/lib/x86_64-linux-gnu/libc.so.6+0x270b2) Address 0x7ffc15eb8028 is located in stack of thread T0 at offset 72
in frame This frame has 1 object(s):
[32, 112) 'q' <== Memory access at offset 72 is inside this variable HINT: this may be a false positive if your program uses some
custom stack unwind mechanism, swapcontext or vfork
(longjmp and C++ exceptions are supported)