From 8e550876b5ffb8054acd9598f86da5fe2dc23621 Mon Sep 17 00:00:00 2001
From: Stoycho Kyosev <stoycho.kk@gmail.com>
Date: Mon, 19 Dec 2022 19:17:32 +0200
Subject: add AVLTree

---
 Seminar10/AVLTree.hpp | 203 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 203 insertions(+)
 create mode 100644 Seminar10/AVLTree.hpp

diff --git a/Seminar10/AVLTree.hpp b/Seminar10/AVLTree.hpp
new file mode 100644
index 0000000..2b4fba7
--- /dev/null
+++ b/Seminar10/AVLTree.hpp
@@ -0,0 +1,203 @@
+#ifndef AVL_TREE_IMPL
+#define AVL_TREE_IMPL
+
+#include<algorithm>
+#include<cassert>
+#include<cstddef>
+
+template<class T>
+class AVLTree {
+private:
+
+	struct Node {
+		T data;
+		Node* left;
+		Node* right;
+		int height;
+
+		static int getHeight(const Node* r) {
+			if (r == nullptr)
+				return 0;
+
+			return r->height;
+		}
+
+		static void rotateLeft(Node*& r) {
+			assert(r->right != nullptr);
+
+			Node* originalRight = r->right;
+			r->right = originalRight->left;
+			originalRight->left = r;
+			r = originalRight;
+		}
+
+		static void rotateRight(Node*& r) {
+			assert(r->left != nullptr);
+
+			Node* originalLeft = r->left;
+			r->left = originalLeft->right;
+			originalLeft->right = r;
+			r = originalLeft;
+		}
+
+		static void balanceLeft(Node*& r) {
+			assert(r);
+
+			int rootBalance = getBalanceFactor(r);
+			int leftBalance = getBalanceFactor(r->left);
+
+			if (rootBalance == -2) {
+				if (leftBalance == 1) {
+					rotateRight(r->left);
+					updateHeight(r->left->left);
+					updateHeight(r->left);
+				}
+
+				rotateLeft(r);
+				updateHeight(r->left);
+				updateHeight(r);
+			}
+		}
+
+		static void balanceRight(Node*& r) {
+			assert(r);
+
+			int rootBalance = getBalanceFactor(r);
+			int rightBalance = getBalanceFactor(r->right);
+
+			if (rootBalance == 2) {
+				if (rightBalance == -1) {
+					rotateRight(r->right);
+					updateHeight(r->right->right);
+					updateHeight(r->right);
+				}
+
+				rotateLeft(r);
+				updateHeight(r->left);
+				updateHeight(r);
+			}
+		}
+
+		static void updateHeight(Node* r) {
+			if (r == nullptr)
+				return;
+			r->height = std::max(getHeight(r->left), getHeight(r->right)) + 1;
+		}
+
+		static int getBalanceFactor(const Node* r) {
+			if (r == nullptr)
+				return 0;
+
+			return getHeight(r->right) - getHeight(r->left);
+		}
+
+		Node(const T& d, Node* l, Node* r, int h) : data{ d }, left{ l }, right{ r }, height{ h } {}
+	};
+
+	Node* findMinNode(Node* r) {
+		if (r->left == nullptr)
+			return r;
+
+		return findMinNode(r->left);
+	}
+
+	void insertRec(Node*& r, const T& elem) {
+		if (r == nullptr) {
+			r = new Node(elem, nullptr, nullptr, 1);
+			size++;
+			return;
+		}
+
+		if (r->data < elem) {
+			insertRec(r->right, elem);
+
+			Node::updateHeight(r->right);
+			Node::balanceRight(r);
+		}
+		else if (r->data > elem) {
+			insertRec(r->left, elem);
+
+			Node::updateHeight(r->left);
+			Node::balanceLeft(r);
+		}
+	}
+
+	bool removeRec(Node*& r, const T& elem) {
+		if (r == nullptr) {
+			return false;
+		}
+
+		if (r->data < elem) {
+			removeRec(r->right, elem);
+
+			Node::updateHeight(r);
+			Node::balanceLeft(r);
+		}
+		else if (r->data > elem) {
+			removeRec(r->left, elem);
+
+			Node::updateHeight(r);
+			Node::balanceRight(r);
+		}
+		else {
+			if (!r->left && !r->right) {
+				delete r;
+				r = nullptr;
+				return true;
+			}
+			else if (r->left && !r->right) {
+				Node* toDelete = r;
+				r = r->left;
+				delete toDelete;
+			}
+			else if (!r->left && r->right) {
+				Node* toDelete = r;
+				r = r->right;
+				delete toDelete;
+			}
+			else {
+				root->data = findMinNode(root->right)->data;
+				removeRec(r->right, r->data);
+				Node::updateHeight(r);
+				Node::balanceRight(r);
+			}
+		}
+		return true;
+	} 
+
+	void freeRec(Node* r) {
+		if (r == nullptr)
+			return;
+
+		freeRec(r->left);
+		freeRec(r->right);
+		delete r;
+	}
+
+public:
+	AVLTree() : root{ nullptr }, size{ 0 } {}
+	
+	// TBI
+	AVLTree(const AVLTree<T>& other) = delete;
+	AVLTree& operator=(const AVLTree<T>& other) = delete;
+	bool contains(const T& elem);
+
+	void insert(const T& elem) {
+		insertRec(root, elem);
+	}
+
+	bool remove(const T& elem) {
+		return removeRec(root, elem);
+	}	
+
+	~AVLTree() {
+		freeRec(root);
+	}
+
+private:
+
+	Node* root;
+	size_t size;
+};
+
+#endif
\ No newline at end of file
-- 
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