TheAlgorithms-C-Plus-Plus/data_structure/AVLtree.cpp

#include <iostream>
#include <queue>

using namespace std;

typedef struct node
{
	int data;
	int height;
	struct node *left;
	struct node *right;
} node;

int max(int a, int b)
{
	return a > b ? a : b;
}

// Returns a new Node

node *createNode(int data)
{
	node *nn = new node();
	nn->data = data;
	nn->height = 0;
	nn->left = NULL;
	nn->right = NULL;
	return nn;
}

// Returns height of tree

int height(node *root)
{
	if (root == NULL)
		return 0;
	return 1 + max(height(root->left), height(root->right));
}

// Returns difference between height of left and right subtree

int getBalance(node *root)
{
	return height(root->left) - height(root->right);
}

// Returns Node after Right Rotation

node *rightRotate(node *root)
{
	node *t = root->left;
	node *u = t->right;
	t->right = root;
	root->left = u;
	return t;
}

// Returns Node after Left Rotation

node *leftRotate(node *root)
{
	node *t = root->right;
	node *u = t->left;
	t->left = root;
	root->right = u;
	return t;
}

// Returns node with minimum value in the tree

node *minValue(node *root)
{
	if (root->left == NULL)
		return root;
	return minValue(root->left);
}

// Balanced Insertion

node *insert(node *root, int item)
{
	node *nn = createNode(item);
	if (root == NULL)
		return nn;
	if (item < root->data)
		root->left = insert(root->left, item);
	else
		root->right = insert(root->right, item);
	int b = getBalance(root);
	if (b > 1)
	{
		if (getBalance(root->left) < 0)
			root->left = leftRotate(root->left); // Left-Right Case
		return rightRotate(root);				 // Left-Left Case
	}
	else if (b < -1)
	{
		if (getBalance(root->right) > 0)
			root->right = rightRotate(root->right); // Right-Left Case
		return leftRotate(root);					// Right-Right Case
	}
	return root;
}

// Balanced Deletion

node *deleteNode(node *root, int key)
{
	if (root == NULL)
		return root;
	if (key < root->data)
		root->left = deleteNode(root->left, key);
	else if (key > root->data)
		root->right = deleteNode(root->right, key);

	else
	{
		// Node to be deleted is leaf node or have only one Child
		if (!root->right)
		{
			node *temp = root->left;
			delete (root);
			root = NULL;
			return temp;
		}
		else if (!root->left)
		{
			node *temp = root->right;
			delete (root);
			root = NULL;
			return temp;
		}
		// Node to be deleted have both left and right subtrees
		node *temp = minValue(root->right);
		root->data = temp->data;
		root->right = deleteNode(root->right, temp->data);
	}
	// Balancing Tree after deletion
	return root;
}

// LevelOrder (Breadth First Search)

void levelOrder(node *root)
{
	queue<node *> q;
	q.push(root);
	while (!q.empty())
	{
		root = q.front();
		cout << root->data << " ";
		q.pop();
		if (root->left)
			q.push(root->left);
		if (root->right)
			q.push(root->right);
	}
}

int main()
{
	// Testing AVL Tree
	node *root = NULL;
	int i;
	for (i = 1; i <= 7; i++)
		root = insert(root, i);
	cout << "LevelOrder: ";
	levelOrder(root);
	root = deleteNode(root, 1); // Deleting key with value 1
	cout << "\nLevelOrder: ";
	levelOrder(root);
	root = deleteNode(root, 4); // Deletin key with value 4
	cout << "\nLevelOrder: ";
	levelOrder(root);
	return 0;
}