#include<iostream>
#include<queue>
#include<sstream>

class TreeNode{
	private:
		TreeNode *left, *right, *parent;
		char data;
	public:
		TreeNode() : left(0), right(0), parent(0), data('x'){};
		TreeNode(char s) : left(0), right(0), parent(0), data(s){};

		friend class BT;
};

class BT{
	private:
		TreeNode *root;
	public:
		BT() : root(0){};
		BT(const char* str){
			std::stringstream ss;
			ss << str;
			root = new TreeNode;
			ss >> root->data;
			BT::LevelorderConstruct(ss);
		}

		void LevelorderConstruct(std::stringstream &ss);
};

void BT::LevelorderConstruct(std::stringstream &ss){

	std::queue<TreeNode*> q;
	TreeNode* current = root;
	char data;

	while (ss >> data){
		if (data != 'x'){
			TreeNode* newNode = new TreeNode(data);
			newNode->parent = current;
			current->left = newNode;
			q.push(newNode);
		}
		if (!(ss >> data))
			break;
		if (data != 'x'){
			TreeNode* newNode = new TreeNode(data);
			newNode->parent = current;
			current->right = newNode;
			q.push(newNode);
		}
		current = q.front();
		q.pop();
	}
}

int main() {
	const char *c = "A B C D x F x H I x K";
	BT BT(c);
	return 0;
}