Iterative In-Order Traversal

• Time : O(n)
• Space : O(1)

#include <vector>
using namespace std;

class BinaryTree {
public:
  int value;
  BinaryTree *left;
  BinaryTree *right;
  BinaryTree *parent;

  BinaryTree(int value, BinaryTree *parent = nullptr);
  void insert(vector<int> values, int i = 0);
};

void iterativeInOrderTraversal(BinaryTree *tree,
                               void (*callback)(BinaryTree *tree)) {
  if(!tree) return;
	iterativeInOrderTraversal(tree->left, callback);
	callback(tree);
	iterativeInOrderTraversal(tree->right, callback);
}