Data Structures: Trees
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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 (currentNode.value > 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 (currentNode.value > value) {
// Left
currentNode = currentNode.left;
} else if (currentNode.value < value) {
// Right
currentNode = currentNode.right;
} else if (currentNode.value === value) {
return currentNode;
}
}
return false;
}
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 (currentNode.value === value) {
//We have a match, get to work!
//Option 1: No right child:
if (currentNode.right === null) {
if (parentNode === null) {
this.root = currentNode.left;
} else {
//if parent > current value, make current left child a child of parent
if (currentNode.value < parentNode.value) {
parentNode.left = currentNode.left;
//if parent < current value, make left child a right child of parent
} else if (currentNode.value > parentNode.value) {
parentNode.right = currentNode.left;
}
}
//Option 2: Right child which doesnt have a left child
} else if (currentNode.right.left === null) {
currentNode.right.left = currentNode.left;
if (parentNode === null) {
this.root = currentNode.right;
} else {
//if parent > current, make right child of the left the parent
if (currentNode.value < parentNode.value) {
parentNode.left = currentNode.right;
//if parent < current, make right child a right child of the parent
} else if (currentNode.value > parentNode.value) {
parentNode.right = currentNode.right;
}
}
//Option 3: Right child that has a left child
} else {
//find the Right child's left most child
let leftmost = currentNode.right.left;
let leftmostParent = currentNode.right;
while (leftmost.left !== null) {
leftmostParent = leftmost;
leftmost = leftmost.left;
}
//Parent's left subtree is now leftmost's right subtree
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 true;
}
}
}
}
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);
tree.remove(170);
JSON.stringify(traverse(tree.root));
console.log(tree.lookup(20));
// 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;
}
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