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BinarySearchTree.java
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235 lines (203 loc) · 5.74 KB
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package com.dsj.trees;
import java.util.ArrayList;
import java.util.List;
import com.dsj.node.Prev_Node_Next;
/**
* The next field of Prev_Node_Next is treated as right child and the prev field
* is treated as the left child.
*/
public class BinarySearchTree<T> {
Prev_Node_Next<T> root;
List<T> listForDelPurpose = new ArrayList<T>();
Prev_Node_Next<T> parent;
Prev_Node_Next<T> toBeProcessedNode;
public BinarySearchTree() {
root = null;
}
/**
* @param dataInNode
* Data in the node. Can be an instance of a number or a string
* @return A new Prev_Node_Next object
*/
private Prev_Node_Next<T> getNewNode(T dataInNode) {
return new Prev_Node_Next<T>(dataInNode);
}
private void insert(Prev_Node_Next<T> parent, T dataInNode) {
if (isEmpty()) {
Prev_Node_Next<T> node = getNewNode(dataInNode);
root = parent = node;
return;
}
/*
* If new node's element is greater than element in parent, insert as
* right child; else, as left child.
*/
if (compare(parent.getDataInNode(), dataInNode) != 1) {
if (parent.getNext() != null) {
parent = parent.getNext();
insert(parent, dataInNode);
} else {
Prev_Node_Next<T> node = getNewNode(dataInNode);
parent.setNext(node);
}
} else {
if (parent.getPrev() != null) {
parent = parent.getPrev();
insert(parent, dataInNode);
} else {
Prev_Node_Next<T> node = getNewNode(dataInNode);
parent.setPrev(node);
}
}
}
private boolean isEmpty() {
return root == null;
}
public void insertNewNode(T dataInNode) {
listForDelPurpose.add(dataInNode);
insert(root, dataInNode);
}
public void deleteNode(T data) {
if (isEmpty()) {
System.out.println("Deletion cannot be performed. The tree is empty.");
return;
}
if (!listForDelPurpose.stream().anyMatch(d -> d.equals(data))) {
System.out.println("Deletion cannot be performed. The tree doesn't have this data.");
return;
}
root = delete(root, data);
}
private Prev_Node_Next<T> delete(Prev_Node_Next<T> ref, T data) {
int compareVal = compare(ref.getDataInNode(), data);
// If parent has greater node value
if (compareVal == 1) {
ref.setPrev(delete(ref.getPrev(), data));
}
// if parent has lesser node value
else if (compareVal == 0) {
ref.setNext(delete(ref.getNext(), data));
}
// If parent's node value and input data are same.
else {
// If the node has one or no child
if (ref.getNext() == null) {
return ref.getPrev();
}
if (ref.getPrev() == null) {
return ref.getNext();
}
// If the node has both children
ref.setDataInNode(minData(ref.getNext()));
ref.setNext(delete(ref.getNext(), ref.getDataInNode()));
}
return ref;
}
private T minData(Prev_Node_Next<T> ref) {
while (ref.getPrev() != null) {
ref = ref.getPrev();
}
return ref.getDataInNode();
}
public void inorderTraversal() {
if (isEmpty()) {
System.out.println("Nothing to show. The tree is empty.");
return;
}
System.out.println("Inorder traversal begins.");
inorder(root);
System.out.println("Inorder traversal ends.");
}
public void preorderTraversal() {
if (isEmpty()) {
System.out.println("Nothing to show. The tree is empty.");
return;
}
System.out.println("Preorder traversal begins.");
preorder(root);
System.out.println("Preorder traversal ends.");
}
public void postOrderTraversal() {
if (isEmpty()) {
System.out.println("Nothing to show. The tree is empty.");
return;
}
System.out.println("Postorder traversal begins.");
postorder(root);
System.out.println("Postorder traversal ends.");
}
private void postorder(Prev_Node_Next<T> parent) {
if (parent.getNext() != null) {
postorder(parent.getNext());
}
if (parent.getPrev() != null) {
postorder(parent.getPrev());
}
System.out.println(parent.getDataInNode());
}
private void inorder(Prev_Node_Next<T> parent) {
if (parent.getPrev() != null) {
inorder(parent.getPrev());
}
System.out.println(parent.getDataInNode());
if (parent.getNext() != null) {
inorder(parent.getNext());
}
}
private void preorder(Prev_Node_Next<T> parent) {
System.out.println(parent.getDataInNode());
if (parent.getPrev() != null) {
preorder(parent.getPrev());
}
if (parent.getNext() != null) {
preorder(parent.getNext());
}
}
/**
* Height of the tree
*/
public void findHeightOfTheTree() {
if (isEmpty()) {
System.out.println("The tree is empty.");
return;
}
System.out.println("Height: " + height(root));
}
private int height(Prev_Node_Next<T> parent) {
int leftHeight = 0;
int rightHeight = 0;
if (parent.getPrev() != null) {
leftHeight = leftHeight + height(parent.getPrev());
}
if (parent.getNext() != null) {
rightHeight = rightHeight + height(parent.getNext());
}
if (rightHeight > leftHeight) {
return rightHeight + 1;
} else {
return leftHeight + 1;
}
}
/**
* Compare the elements of current parent and new node
*/
public int compare(T parentData, T inputData) {
int result = -1;
if (parentData instanceof String) {
if (((String) parentData).length() > ((String) inputData).length()) {
result = 1;
} else if (((String) parentData).length() < ((String) inputData).length()) {
result = 0;
}
}
if (parentData instanceof Number) {
if (((Number) parentData).doubleValue() > ((Number) inputData).doubleValue()) {
result = 1;
} else if (((Number) parentData).doubleValue() < ((Number) inputData).doubleValue()) {
result = 0;
}
}
// result will contain -1 if both values are same.
return result;
}
}