rb_tree.cpp

#include<iostream>

using namespace std;

struct node
{
	int key;
	node *parent;
	char color;
	node *left;
	node *right;
};
class RBtree
{
	node *root;
	node *q;
public:
	RBtree()
	{
		q = NULL;
		root = NULL;
	}
	void insert();
	void insertfix(node *);
	void leftrotate(node *);
	void rightrotate(node *);
	void del();
	node* successor(node *);
	void delfix(node *);
	void disp();
	void display(node *);
	void search();
};
void RBtree::insert()
{
	int z, i = 0;
	cout << "\nEnter key of the node to be inserted: ";
	cin >> z;
	node *p, *q;
	node *t = new node;
	t->key = z;
	t->left = NULL;
	t->right = NULL;
	t->color = 'r';
	p = root;
	q = NULL;
	if (root == NULL)
	{
		root = t;
		t->parent = NULL;
	}
	else
	{
		while (p != NULL)
		{
			q = p;
			if (p->key < t->key)
				p = p->right;
			else
				p = p->left;
		}
		t->parent = q;
		if (q->key < t->key)
			q->right = t;
		else
			q->left = t;
	}
	insertfix(t);
}
void RBtree::insertfix(node *t)
{
	node *u;
	if (root == t)
	{
		t->color = 'b';
		return;
	}
	while (t->parent != NULL && t->parent->color == 'r')
	{
		node *g = t->parent->parent;
		if (g->left == t->parent)
		{
			if (g->right != NULL)
			{
				u = g->right;
				if (u->color == 'r')
				{
					t->parent->color = 'b';
					u->color = 'b';
					g->color = 'r';
					t = g;
				}
			}
			else
			{
				if (t->parent->right == t)
				{
					t = t->parent;
					leftrotate(t);
				}
				t->parent->color = 'b';
				g->color = 'r';
				rightrotate(g);
			}
		}
		else
		{
			if (g->left != NULL)
			{
				u = g->left;
				if (u->color == 'r')
				{
					t->parent->color = 'b';
					u->color = 'b';
					g->color = 'r';
					t = g;
				}
			}
			else
			{
				if (t->parent->left == t)
				{
					t = t->parent;
					rightrotate(t);
				}
				t->parent->color = 'b';
				g->color = 'r';
				leftrotate(g);
			}
		}
		root->color = 'b';
	}
}

void RBtree::del()
{
	if (root == NULL)
	{
		cout << "\nEmpty Tree.";
		return;
	}
	int x;
	cout << "\nEnter the key of the node to be deleted: ";
	cin >> x;
	node *p;
	p = root;
	node *y = NULL;
	node *q = NULL;
	int found = 0;
	while (p != NULL && found == 0)
	{
		if (p->key == x)
			found = 1;
		if (found == 0)
		{
			if (p->key < x)
				p = p->right;
			else
				p = p->left;
		}
	}
	if (found == 0)
	{
		cout << "\nElement Not Found.";
		return;
	}
	else
	{
		cout << "\nDeleted Element: " << p->key;
		cout << "\nColour: ";
		if (p->color == 'b')
			cout << "Black\n";
		else
			cout << "Red\n";

		if (p->parent != NULL)
			cout << "\nParent: " << p->parent->key;
		else
			cout << "\nThere is no parent of the node.  ";
		if (p->right != NULL)
			cout << "\nRight Child: " << p->right->key;
		else
			cout << "\nThere is no right child of the node.  ";
		if (p->left != NULL)
			cout << "\nLeft Child: " << p->left->key;
		else
			cout << "\nThere is no left child of the node.  ";
		cout << "\nNode Deleted.";
		if (p->left == NULL || p->right == NULL)
			y = p;
		else
			y = successor(p);
		if (y->left != NULL)
			q = y->left;
		else
		{
			if (y->right != NULL)
				q = y->right;
			else
				q = NULL;
		}
		if (q != NULL)
			q->parent = y->parent;
		if (y->parent == NULL)
			root = q;
		else
		{
			if (y == y->parent->left)
				y->parent->left = q;
			else
				y->parent->right = q;
		}
		if (y != p)
		{
			p->color = y->color;
			p->key = y->key;
		}
		if (y->color == 'b')
			delfix(q);
	}
}

void RBtree::delfix(node *p)
{
	node *s;
	while (p != root && p->color == 'b')
	{
		if (p->parent->left == p)
		{
			s = p->parent->right;
			if (s->color == 'r')
			{
				s->color = 'b';
				p->parent->color = 'r';
				leftrotate(p->parent);
				s = p->parent->right;
			}
			if (s->right->color == 'b'&&s->left->color == 'b')
			{
				s->color = 'r';
				p = p->parent;
			}
			else
			{
				if (s->right->color == 'b')
				{
					s->left->color = 'b';
					s->color = 'r';
					rightrotate(s);
					s = p->parent->right;
				}
				s->color = p->parent->color;
				p->parent->color = 'b';
				s->right->color = 'b';
				leftrotate(p->parent);
				p = root;
			}
		}
		else
		{
			s = p->parent->left;
			if (s->color == 'r')
			{
				s->color = 'b';
				p->parent->color = 'r';
				rightrotate(p->parent);
				s = p->parent->left;
			}
			if (s->left->color == 'b'&&s->right->color == 'b')
			{
				s->color = 'r';
				p = p->parent;
			}
			else
			{
				if (s->left->color == 'b')
				{
					s->right->color = 'b';
					s->color = 'r';
					leftrotate(s);
					s = p->parent->left;
				}
				s->color = p->parent->color;
				p->parent->color = 'b';
				s->left->color = 'b';
				rightrotate(p->parent);
				p = root;
			}
		}
		p->color = 'b';
		root->color = 'b';
	}
}

void RBtree::leftrotate(node *p)
{
	if (p->right == NULL)
		return;
	else
	{
		node *y = p->right;
		if (y->left != NULL)
		{
			p->right = y->left;
			y->left->parent = p;
		}
		else
			p->right = NULL;
		if (p->parent != NULL)
			y->parent = p->parent;
		if (p->parent == NULL)
			root = y;
		else
		{
			if (p == p->parent->left)
				p->parent->left = y;
			else
				p->parent->right = y;
		}
		y->left = p;
		p->parent = y;
	}
}
void RBtree::rightrotate(node *p)
{
	if (p->left == NULL)
		return;
	else
	{
		node *y = p->left;
		if (y->right != NULL)
		{
			p->left = y->right;
			y->right->parent = p;
		}
		else
			p->left = NULL;
		if (p->parent != NULL)
			y->parent = p->parent;
		if (p->parent == NULL)
			root = y;
		else
		{
			if (p == p->parent->left)
				p->parent->left = y;
			else
				p->parent->right = y;
		}
		y->right = p;
		p->parent = y;
	}
}

node* RBtree::successor(node *p)
{
	node *y = NULL;
	if (p->left != NULL)
	{
		y = p->left;
		while (y->right != NULL)
			y = y->right;
	}
	else
	{
		y = p->right;
		while (y->left != NULL)
			y = y->left;
	}
	return y;
}

void RBtree::disp()
{
	display(root);
}
void RBtree::display(node *p)
{
	if (root == NULL)
	{
		cout << "\nEmpty Tree.";
		return;
	}
	if (p != NULL)
	{
		cout << "\n\t NODE: ";
		cout << "\n Key: " << p->key;
		cout << "\n Colour: ";
		if (p->color == 'b')
			cout << "Black";
		else
			cout << "Red";
		if (p->parent != NULL)
			cout << "\n Parent: " << p->parent->key;
		else
			cout << "\n There is no parent of the node.  ";
		if (p->right != NULL)
			cout << "\n Right Child: " << p->right->key;
		else
			cout << "\n There is no right child of the node.  ";
		if (p->left != NULL)
			cout << "\n Left Child: " << p->left->key;
		else
			cout << "\n There is no left child of the node.  ";
		cout << endl;
		if (p->left)
		{
			cout << "\n\nLeft:\n";
			display(p->left);
		}
		/*else
		 cout<<"\nNo Left Child.\n";*/
		if (p->right)
		{
			cout << "\n\nRight:\n";
			display(p->right);
		}
		/*else
		 cout<<"\nNo Right Child.\n"*/
	}
}
void RBtree::search()
{
	if (root == NULL)
	{
		cout << "\nEmpty Tree\n";
		return;
	}
	int x;
	cout << "\n Enter key of the node to be searched: ";
	cin >> x;
	node *p = root;
	int found = 0;
	while (p != NULL && found == 0)
	{
		if (p->key == x)
			found = 1;
		if (found == 0)
		{
			if (p->key < x)
				p = p->right;
			else
				p = p->left;
		}
	}
	if (found == 0)
		cout << "\nElement Not Found.";
	else
	{
		cout << "\n\t FOUND NODE: ";
		cout << "\n Key: " << p->key;
		cout << "\n Colour: ";
		if (p->color == 'b')
			cout << "Black";
		else
			cout << "Red";
		if (p->parent != NULL)
			cout << "\n Parent: " << p->parent->key;
		else
			cout << "\n There is no parent of the node.  ";
		if (p->right != NULL)
			cout << "\n Right Child: " << p->right->key;
		else
			cout << "\n There is no right child of the node.  ";
		if (p->left != NULL)
			cout << "\n Left Child: " << p->left->key;
		else
			cout << "\n There is no left child of the node.  ";
		cout << endl;

	}
}
int main()
{
	int ch, y = 0;
	RBtree obj;
	do
	{
		cout << "\n\t RED BLACK TREE ";
		cout << "\n 1. Insert in the tree ";
		cout << "\n 2. Delete a node from the tree";
		cout << "\n 3. Search for an element in the tree";
		cout << "\n 4. Display the tree ";
		cout << "\n 5. Exit ";
		cout << "\nEnter Your Choice: ";
		cin >> ch;
		switch (ch)
		{
		case 1: obj.insert();
			cout << "\nNode Inserted.\n";
			break;
		case 2: obj.del();
			break;
		case 3: obj.search();
			break;
		case 4: obj.disp();
			break;
		case 5: y = 1;
			break;
		default: cout << "\nEnter a Valid Choice.";
		}
		cout << endl;

	} while (y != 1);
	return 1;
}