AVL Tree node deletion - c++

Question

I was trying to implement AVL Tree in C++, I Implemented key insertion without much problem but while trying to delete a node I ran into use after free bug. I tried to debug with gdb but I was unable to find out the problem, Here's the full code.
#include <iostream>
#include <algorithm>
using namespace std;
class Node;
class AVLTree;
typedef Node* node_ptr;
class Node {
int key;
int height;
node_ptr left;
node_ptr right;
void fix_height() {
int hR, hL = 0;
if (left) hL = left->height;
if (right) hR = right->height;
height = max(hL, hR) + 1;
}
int balance_factor() {
if (left && right)
return left->height - right->height;
if (left && !right)
return left->height;
if (right && !left)
return -right->height;
return 0;
}
public:
Node(int key) :key(key), left(nullptr), right(nullptr),height(1){}
friend class AVLTree;
};
class AVLTree {
node_ptr mRoot;
node_ptr insert(node_ptr node, int key) {
if (!node) return new Node(key);
if (node->key > key) node->left = insert(node->left, key);
else node->right = insert(node->right, key);
return balance(node);
}
node_ptr left_rotate(node_ptr X) {
node_ptr Y = X->right;
X->right = Y->left;
Y->left = X;
X->fix_height();
Y->fix_height();
return Y;
}
node_ptr right_rotate(node_ptr Y) {
node_ptr X = Y->left;
Y->left = X->right;
X->right = Y;
X->fix_height();
Y->fix_height();
return X;
}
node_ptr balance(node_ptr node) {
node->fix_height();
int b_factor = node->balance_factor();
if (b_factor == 2) {
if (node->left->balance_factor() < 0) {
node->left = left_rotate(node->left);
}
return right_rotate(node);
}
else if (b_factor == -2) {
if (node->right->balance_factor() > 0) {
node->right = right_rotate(node->right);
}
return left_rotate(node);
}
return node;
}
node_ptr find_min(node_ptr node) {
if (!node) return nullptr;
if (!node->left) return node;
else return
find_min(node->left);
}
node_ptr remove_min(node_ptr node) {
if (!node->left)
return node->right;
node->left = remove_min(node->left);
return balance(node);
}
node_ptr remove(node_ptr node, int key) {
if (!node) return nullptr;
if (node->key > key)
node->left = remove(node->left, key);
else if (node->key < key)
node->right = remove(node->right, key);
else {
node_ptr L = node->left;
node_ptr R = node->right;
delete node;
if (!R) return L;
node_ptr min = find_min(node->right);
min->right = remove_min(R);
min->left = L;
return balance(min);
}
return balance(node);
}
void print_inorder(node_ptr node) {
if (node) {
print_inorder(node->left);
cout << node->key << " ";
print_inorder(node->right);
}
}
public:
AVLTree() :mRoot(nullptr) {}
void insert(int key) {
mRoot = insert(mRoot, key);
}
void remove(int key) {
mRoot = remove(mRoot, key);
}
void print_inorder() {
cout << endl;
print_inorder(mRoot);
cout << endl;
}
};
int main()
{
AVLTree mtree;
for (int i = 0; i < 3; ++i) {
mtree.insert(i);
}
mtree.remove(0);
mtree.remove(1);
mtree.remove(2);
mtree.print_inorder();
return 0;
}
So, In remove_min(), I am using the same logic as a binary search tree. If sub-tree has a right child, minimum element from that right subtree is returned, and replaced with the target node, If not then just pointer to left subtree is returned and as function returns it balances the disturbed nodes. But somehow deleted node is getting referenced and I am getting segmentation fault. I cannot figure out how. Can someone help ?