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index.js
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const Node = require('./Node');
class BinarySearchTree {
constructor(value) {
this.root = new Node(value);
}
insert(root, value) {
if (root === null) {
const newNode = new Node(value);
// eslint-disable-next-line no-param-reassign
root = newNode;
return root;
}
if (value < root.value) {
// eslint-disable-next-line no-param-reassign
root.leftChild = this.insert(root.leftChild, value);
return root;
}
if (value > root.value) {
// eslint-disable-next-line no-param-reassign
root.rightChild = this.insert(root.rightChild, value);
return root;
}
return root;
}
preorder(root) {
/** returning an array so as to make testing easy */
let arr = [];
if (root === null) return [];
arr.push(root.value);
const left = this.preorder(root.leftChild);
arr = [...arr, ...left];
const right = this.preorder(root.rightChild);
arr = [...arr, ...right];
return arr;
}
inorder(root) {
/** left - root - right */
if (root === null) return [];
let arr = [];
const left = this.inorder(root.leftChild);
arr = [...left, ...arr];
// print root
arr = [...arr, root.value];
const right = this.inorder(root.rightChild);
arr = [...arr, ...right];
return arr;
}
postorder(root) {
/** left - right - root */
if (root === null) return [];
let arr = [];
const left = this.postorder(root.leftChild);
arr = [...left, ...arr];
const right = this.postorder(root.rightChild);
arr = [...arr, ...right];
return [...arr, root.value];
}
search(root, value) {
if (root === null) return false;
if (value === root.value) return true;
if (value < root.value) {
return this.search(root.leftChild, value);
}
if (value > root.value) {
return this.search(root.rightChild, value);
}
return false;
}
isEmpty() {
return this.root === null;
}
/** Layered methods to simplify the BST API */
add(value) {
return this.insert(this.root, value);
}
traversePreorder() {
return this.preorder(this.root);
}
traversePostorder() {
return this.postorder(this.root);
}
traverseInorder() {
return this.inorder(this.root);
}
searchFor(value) {
return this.search(this.root, value);
}
}
// const bst = new BinarySearchTree(6);
// console.log(bst.root);
// bst.add(4);
// bst.add(9);
// bst.add(2);
// bst.add(5);
// bst.add(8);
// bst.add(12);
// console.log(bst.root);
// const preorder = bst.traversePreorder();
// console.log('Preorder Traversal - ', preorder);
// const inorder = bst.traverseInorder();
// console.log('Inorder Traversal - ', inorder);
// const postorder = bst.traversePostorder();
// console.log('Postorder Traversal - ', postorder);
// const search = 18;
// console.log(`Search for ${search}`, bst.searchFor(search));
module.exports = BinarySearchTree;