package com.thealgorithms.datastructures.trees;
import com.thealgorithms.datastructures.trees.BinaryTree.Node;
/**
*
*
* <h1>Binary Search Tree (Iterative)</h1>
*
* <p>
* An implementation of BST iteratively. Binary Search Tree is a binary tree
* which satisfies three properties: left child is less than root node, right
* child is grater than root node, both left and right child must themselves be
* a BST.
*
* @author [Lakhan Nad](<a href="https://github.com/Lakhan-Nad">git-Lakhan Nad</a>)
*/
public class BSTIterative {
/**
* Reference for the node of BST.
*/
private Node root;
/**
* Default Constructor Initializes the root of BST with null.
*/
BSTIterative() {
root = null;
}
public Node getRoot() {
return root;
}
/**
* A method to insert a new value in BST. If the given value is already
* present in BST the insertion is ignored.
*
* @param data the value to be inserted
*/
public void add(int data) {
Node parent = null;
Node temp = this.root;
int rightOrLeft = -1;
/* Finds the proper place this node can
* be placed in according to rules of BST.
*/
while (temp != null) {
if (temp.data > data) {
parent = temp;
temp = parent.left;
rightOrLeft = 0;
} else if (temp.data < data) {
parent = temp;
temp = parent.right;
rightOrLeft = 1;
} else {
System.out.println(data + " is already present in BST.");
return; // if data already present we ignore insertion
}
}
/* Creates a newNode with the value passed
* Since this data doesn't already exists
*/
Node newNode = new Node(data);
/* If the parent node is null
* then the insertion is to be done in
* root itself.
*/
if (parent == null) {
this.root = newNode;
} else {
/* Check if insertion is to be made in
* left or right subtree.
*/
if (rightOrLeft == 0) {
parent.left = newNode;
} else {
parent.right = newNode;
}
}
}
/**
* A method to delete the node in BST. If node is present it will be deleted
*
* @param data the value that needs to be deleted
*/
public void remove(int data) {
Node parent = null;
Node temp = this.root;
int rightOrLeft = -1;
/* Find the parent of the node and node itself
* That is to be deleted.
* parent variable store parent
* temp stores node itself.
* rightOrLeft use to keep track weather child
* is left or right subtree
*/
while (temp != null) {
if (temp.data == data) {
break;
} else if (temp.data > data) {
parent = temp;
temp = parent.left;
rightOrLeft = 0;
} else {
parent = temp;
temp = parent.right;
rightOrLeft = 1;
}
}
/* If temp is null than node with given value is not
* present in our tree.
*/
if (temp != null) {
Node replacement; // used to store the new values for replacing nodes
if (temp.right == null && temp.left == null) { // Leaf node Case
replacement = null;
} else if (temp.right == null) { // Node with only right child
replacement = temp.left;
temp.left = null;
} else if (temp.left == null) { // Node with only left child
replacement = temp.right;
temp.right = null;
} else {
/* If both left and right child are present
* we replace this nodes data with
* leftmost node's data in its right subtree
* to maintain the balance of BST.
* And then delete that node
*/
if (temp.right.left == null) {
temp.data = temp.right.data;
replacement = temp;
temp.right = temp.right.right;
} else {
Node parent2 = temp.right;
Node child = temp.right.left;
while (child.left != null) {
parent2 = child;
child = parent2.left;
}
temp.data = child.data;
parent2.left = child.right;
replacement = temp;
}
}
/* Change references of parent after
* deleting the child.
*/
if (parent == null) {
this.root = replacement;
} else {
if (rightOrLeft == 0) {
parent.left = replacement;
} else {
parent.right = replacement;
}
}
}
}
/**
* A method to check if given data exists in out Binary Search Tree.
*
* @param data the value that needs to be searched for
* @return boolean representing if the value was find
*/
public boolean find(int data) {
Node temp = this.root;
/* Check if node exists
*/
while (temp != null) {
if (temp.data > data) {
temp = temp.left;
} else if (temp.data < data) {
temp = temp.right;
} else {
/* If found return true
*/
System.out.println(data + " is present in the BST.");
return true;
}
}
System.out.println(data + " not found.");
return false;
}
}