Implementation of Binary Search Tree
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class Node {
constructor(value){
this.left = null;
this.right = null;
this.value = value;
}
}
class BinarySearchTree {
constructor(){
this.root = null;
}
insert(value){
const newNode = new Node(value);
if (this.root === null) {
this.root = newNode;
} else {
let currentNode = this.root;
while(true){
if(value < currentNode.value){
//Left
if(!currentNode.left){
currentNode.left = newNode;
return this;
}
currentNode = currentNode.left;
} else {
//Right
if(!currentNode.right){
currentNode.right = newNode;
return this;
}
currentNode = currentNode.right;
}
}
}
}
lookup(value){
if (!this.root) {
return false;
}
let currentNode = this.root;
while(currentNode){
if(value < currentNode.value){
currentNode = currentNode.left;
} else if(value > currentNode.value){
currentNode = currentNode.right;
} else if (currentNode.value === value) {
return currentNode;
}
}
return null
}
// remove
remove(value){
if(!this.root){
return false;
}
let currentNode=this.root;
let parentNode=null;
while(currentNode){
if(value<currentNode.value){
parentNode=currentNode;
currentNode=currentNode.left;
}
else if (value>currentNode.value){
parentNode=currentNode;
currentNode=currentNode.right;
}
else if(value===currentNode.value){
//if it has no right child
if(currentNode.right===null){
if(parentNode===null){
this.root=currentNode.left
}else{
if(currentNode.value<parentNode.value){
parentNode.left=currentNode.left;
}
else if(currentNode.value>parentNode.value){
parentNode.right=currentNode.left;
}
}
}
else if(currentNode.right.left===null){
currentNode.right.left=currentNode.left;
if(parentNode===null){
this.root=currentNode.right;
}
else{
if(currentNode.value<parentNode.value){
parentNode.left=currentNode.right;
}
else if(currentNode.value>parentNode.value){
parentNode.right=currentNode.right
}
else{
let leftmost=currentNode.right.left;
let leftmostParent=currentNode.right;
while(leftmost!==null){
leftmostParent=leftmost;
leftmost=leftmost.left;
}
leftmostParent.left=leftmost.right;
leftmost.left=currentNode.left;
leftmost.right=currentNode.right;
if(parentNode===null){
this.root=leftmost;
}
else{
if(currentNode.value<parentNode.value){
parentNode.left=leftmost;
}
else if(currentNode.value>parentNode.value){
parentNode.right=leftmost;
}
}
}
return false;
}
}
}
}
}
}
const tree = new BinarySearchTree();
tree.insert(9)
tree.insert(4)
tree.insert(6)
tree.insert(20)
tree.insert(170)
tree.insert(15)
tree.insert(1)
// JSON.stringify(traverse(tree.root))
tree.lookup(15);
tree.lookup(7);
// 9
// 4 20
//1 6 15 170
function traverse(node) {
const tree = { value: node.value };
tree.left = node.left === null ? null : traverse(node.left);
tree.right = node.right === null ? null : traverse(node.right);
return tree;
}
JavaScript
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