[Mine] Binary Tree Traversal

InterviewerAnswer.cpp

#include <iostream>

//==RELATED TO INTERVIEW==
//Q: Return next element (if 9, return 11), -2 if next element doesn't exist, -1 if element itself doesn't exist
struct Node {
	Node *left = nullptr;
	Node *parent = nullptr;
	Node *right = nullptr;
	int value = 0;
};

int sorted[8];
int sorted_it = 0;

void traverse(Node* parent_node) {
	if (parent_node->left != nullptr)
		traverse(parent_node->left);

	*(sorted + sorted_it++) = parent_node->value;

	if (parent_node->right != nullptr)
		traverse(parent_node->right);
}

int binarySearchNext(int* list, int list_size, int element) {
	int *start = list, *end = list + list_size -1; 
	int* it;

	if (*end == element) //next element cannot exist
		return -2;

	while (true) {
		it = start + (end - start) / 2; //get middle everytime
		if (*it == element) {
			it++;
			break;
		}	

		if (*it < element)
			start = it;

		if (*it > element)
			end = it;

		if (it == start)
			return -1; //can't even find the element
	}

	return *it;
}


//===NOT RELATED TO INTERVIEW===
void insert(Node* parent_node, int val) {
	if (val < parent_node->value) { //less
		if (parent_node->left == nullptr)
			parent_node->left = new Node{nullptr, nullptr, nullptr, val};
		else insert(parent_node->left, val);	
	}

	if (val > parent_node->value) { //more
		if (parent_node->right == nullptr)
			parent_node->right = new Node{nullptr, nullptr, nullptr, val};
		else insert(parent_node->right, val);
	}
}

int main() {
	//create tree
	int numbers[] = {15, 10, 9, 11, 20, 19, 23, 25};	
	Node *parent_node = new Node{nullptr, nullptr, nullptr, numbers[0]};

	for (int i = 1; i < 8; i++)
		insert(parent_node, numbers[i]);

	traverse(parent_node);
	std::cout << binarySearchNext(sorted, 8, 11) << std::endl;

	return 0;
}

MyAnswer.cpp

#include <iostream>

//==RELATED TO INTERVIEW==
//Q: Return next element (if 9, return 11), -2 if next element doesn't exist, -1 if element itself doesn't exist
struct Node {
	Node *left = nullptr;
	Node *parent = nullptr;
	Node *right = nullptr;
	int value = 0;
};

bool element_found = false;
Node* nextElementNode = nullptr; //answer will be here 

void traverse(Node* parent_node, int num) {
	if (parent_node->left != nullptr)
		traverse(parent_node->left, num);

	if (element_found)
		if (nextElementNode == nullptr)
			nextElementNode = parent_node;
		else return;

	if (num == parent_node->value)
		element_found = true;
	
	if (parent_node->right != nullptr)
		traverse(parent_node->right, num);
}

int findNextElement(Node* parent_node, int num) {
	traverse(parent_node, num);

	if (element_found && nextElementNode == nullptr)
		return -2;
	
	if (!element_found && nextElementNode == nullptr)
		return -1;

	return nextElementNode->value;
}

//===NOT RELATED TO INTERVIEW===
void insert(Node* parent_node, int val) {
	if (val < parent_node->value) { //less
		if (parent_node->left == nullptr)
			parent_node->left = new Node{nullptr, nullptr, nullptr, val};
		else insert(parent_node->left, val);	
	}

	if (val > parent_node->value) { //more
		if (parent_node->right == nullptr)
			parent_node->right = new Node{nullptr, nullptr, nullptr, val};
		else insert(parent_node->right, val);
	}
}

int main() {
	//create tree
	int numbers[] = {15, 10, 9, 11, 20, 19, 23, 25};	
	Node *parent_node = new Node{nullptr, nullptr, nullptr, numbers[0]};

	for (int i = 1; i < 8; i++)
		insert(parent_node, numbers[i]);

	std::cout << findNextElement(parent_node, 11) << std::endl;

	return 0;
}