Add AVL Tree.

This commit is contained in:
Oleksii Trekhleb 2018-04-06 09:11:08 +03:00
parent 81253e8a5d
commit d10293c088
2 changed files with 287 additions and 0 deletions

View File

@ -0,0 +1,122 @@
import BinarySearchTree from '../binary-search-tree/BinarySearchTree';
export default class AvlTree extends BinarySearchTree {
insert(value) {
// Do the normal BST insert.
super.insert(value);
// Let's move up to the root and check balance factors along the way.
let currentNode = this.root.find(value);
while (currentNode) {
this.balance(currentNode);
currentNode = currentNode.parent;
}
}
balance(node) {
// If balance factor is not OK then try to balance the node.
if (node.balanceFactor > 1) {
// Left rotation.
if (node.left.balanceFactor > 0) {
// Left-Left rotation
this.rotateLeftLeft(node);
} else if (node.left.balanceFactor < 0) {
// Left-Right rotation.
this.rotateLeftRight(node);
}
} else if (node.balanceFactor < -1) {
// Right rotation.
if (node.right.balanceFactor < 0) {
// Right-Right rotation
this.rotateRightRight(node);
} else if (node.right.balanceFactor > 0) {
// Right-Left rotation.
this.rotateRightLeft(node);
}
}
}
rotateLeftLeft(rootNode) {
// Detach left node from root node.
const leftNode = rootNode.left;
rootNode.setLeft(null);
// Make left node to be a child of rootNode's parent.
if (rootNode.parent) {
rootNode.parent.setLeft(leftNode);
} else if (rootNode === this.root) {
// If root node is root then make left node to be a new root.
this.root = leftNode;
}
// If left node has a right child then detach it and
// attach it as a left child for rootNode.
if (leftNode.right) {
rootNode.setLeft(leftNode.right);
}
// Attach rootNode to the right of leftNode.
leftNode.setRight(rootNode);
}
rotateLeftRight(rootNode) {
// Detach left node from rootNode since it is going to be replaced.
const leftNode = rootNode.left;
rootNode.setLeft(null);
// Detach right node from leftNode.
const leftRightNode = leftNode.right;
leftNode.setRight(null);
// Attach leftRightNode to the rootNode.
rootNode.setLeft(leftRightNode);
// Attach leftNode as left node for leftRight node.
leftRightNode.setLeft(leftNode);
// Do left-left rotation.
this.rotateLeftLeft(rootNode);
}
rotateRightLeft(rootNode) {
// Detach right node from rootNode since it is going to be replaced.
const rightNode = rootNode.right;
rootNode.setRight(null);
// Detach left node from rightNode.
const rightLeftNode = rightNode.left;
rightNode.setLeft(null);
// Attach rightLeftNode to the rootNode.
rootNode.setRight(rightLeftNode);
// Attach rightNode as right node for rightLeft node.
rightLeftNode.setRight(rightNode);
// Do right-right rotation.
this.rotateRightRight(rootNode);
}
rotateRightRight(rootNode) {
// Detach right node from root node.
const rightNode = rootNode.right;
rootNode.setRight(null);
// Make right node to be a child of rootNode's parent.
if (rootNode.parent) {
rootNode.parent.setRight(rightNode);
} else if (rootNode === this.root) {
// If root node is root then make right node to be a new root.
this.root = rightNode;
}
// If right node has a left child then detach it and
// attach it as a right child for rootNode.
if (rightNode.left) {
rootNode.setRight(rightNode.left);
}
// Attach rootNode to the left of rightNode.
rightNode.setLeft(rootNode);
}
}

View File

@ -0,0 +1,165 @@
import AvlTree from '../AvlTree';
describe('AvlTree', () => {
it('should do simple left-left rotation', () => {
const tree = new AvlTree();
tree.insert(4);
tree.insert(3);
tree.insert(2);
expect(tree.toString()).toBe('2,3,4');
expect(tree.root.value).toBe(3);
expect(tree.root.height).toBe(1);
tree.insert(1);
expect(tree.toString()).toBe('1,2,3,4');
expect(tree.root.value).toBe(3);
expect(tree.root.height).toBe(2);
tree.insert(0);
expect(tree.toString()).toBe('0,1,2,3,4');
expect(tree.root.value).toBe(3);
expect(tree.root.left.value).toBe(1);
expect(tree.root.height).toBe(2);
});
it('should do complex left-left rotation', () => {
const tree = new AvlTree();
tree.insert(30);
tree.insert(20);
tree.insert(40);
tree.insert(10);
expect(tree.root.value).toBe(30);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('10,20,30,40');
tree.insert(25);
expect(tree.root.value).toBe(30);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('10,20,25,30,40');
tree.insert(5);
expect(tree.root.value).toBe(20);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('5,10,20,25,30,40');
});
it('should do simple right-right rotation', () => {
const tree = new AvlTree();
tree.insert(2);
tree.insert(3);
tree.insert(4);
expect(tree.toString()).toBe('2,3,4');
expect(tree.root.value).toBe(3);
expect(tree.root.height).toBe(1);
tree.insert(5);
expect(tree.toString()).toBe('2,3,4,5');
expect(tree.root.value).toBe(3);
expect(tree.root.height).toBe(2);
tree.insert(6);
expect(tree.toString()).toBe('2,3,4,5,6');
expect(tree.root.value).toBe(3);
expect(tree.root.right.value).toBe(5);
expect(tree.root.height).toBe(2);
});
it('should do complex right-right rotation', () => {
const tree = new AvlTree();
tree.insert(30);
tree.insert(20);
tree.insert(40);
tree.insert(50);
expect(tree.root.value).toBe(30);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('20,30,40,50');
tree.insert(35);
expect(tree.root.value).toBe(30);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('20,30,35,40,50');
tree.insert(55);
expect(tree.root.value).toBe(40);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('20,30,35,40,50,55');
});
it('should do left-right rotation', () => {
const tree = new AvlTree();
tree.insert(30);
tree.insert(20);
tree.insert(25);
expect(tree.root.height).toBe(1);
expect(tree.root.value).toBe(25);
expect(tree.toString()).toBe('20,25,30');
});
it('should do right-left rotation', () => {
const tree = new AvlTree();
tree.insert(30);
tree.insert(40);
tree.insert(35);
expect(tree.root.height).toBe(1);
expect(tree.root.value).toBe(35);
expect(tree.toString()).toBe('30,35,40');
});
it('should create balanced tree: case #1', () => {
const tree = new AvlTree();
tree.insert(1);
tree.insert(2);
tree.insert(3);
expect(tree.root.value).toBe(2);
expect(tree.root.height).toBe(1);
expect(tree.toString()).toBe('1,2,3');
tree.insert(6);
expect(tree.root.value).toBe(2);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('1,2,3,6');
tree.insert(15);
expect(tree.root.value).toBe(2);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('1,2,3,6,15');
tree.insert(-2);
expect(tree.root.value).toBe(2);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('-2,1,2,3,6,15');
tree.insert(-5);
expect(tree.root.value).toBe(2);
expect(tree.root.height).toBe(2);
expect(tree.toString()).toBe('-5,-2,1,2,3,6,15');
tree.insert(-8);
expect(tree.root.value).toBe(2);
expect(tree.root.height).toBe(3);
expect(tree.toString()).toBe('-8,-5,-2,1,2,3,6,15');
});
});