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tree-rotations.spec.js
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tree-rotations.spec.js
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const BinaryTreeNode = require('./binary-tree-node');
const {
leftRotation,
rightRotation,
leftRightRotation,
rightLeftRotation,
} = require('./tree-rotations');
describe('Tree rotations', () => {
let n1;
let n2;
let n3;
let n4;
beforeEach(() => {
n1 = new BinaryTreeNode(1);
n2 = new BinaryTreeNode(2);
n3 = new BinaryTreeNode(3);
n4 = new BinaryTreeNode(4);
});
describe('#leftRotation (LL Rotation)', () => {
it('basic LL rotation', () => {
/*
* 1* 2*
* \ / \
* 2 ---| left-rotation(1) |--> 1 3
* \
* 3
*/
n1.setRightAndUpdateParent(n2);
n2.setRightAndUpdateParent(n3);
const newParent = leftRotation(n1);
expect(newParent.value).toBe(2);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: null, parent: 2,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: 1, right: 3, parent: null,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: null, right: null, parent: 2,
});
});
it('should rotate left with root (LL Rotation)', () => {
// 1
// \
// 2*
// \
// 3
// \
// 4
n1.setRightAndUpdateParent(n2);
n2.setRightAndUpdateParent(n3);
n3.setRightAndUpdateParent(n4);
const newParent = leftRotation(n2);
expect(newParent).toBe(n3);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: 3, parent: null,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: null, right: null, parent: 3,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: 2, right: 4, parent: 1,
});
});
it('should rotate last two', () => {
// 4
// /
// 3
// /
// 1*
// \
// 2
n4.setLeftAndUpdateParent(n3);
n3.setLeftAndUpdateParent(n1);
n1.setRightAndUpdateParent(n2);
const newParent = leftRotation(n1);
expect(newParent).toBe(n2);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: null, parent: 2,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: 1, right: null, parent: 3,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: 2, right: null, parent: 4,
});
});
it('should not lose nodes on LL', () => {
// 1 1
// \ \
// 4* 16
// / \ / \
// 2 16 -- left-rotation(4) -> 4 32
// / \ / \ \
// 8 32 2 8 64
// \
// 64
const n8 = new BinaryTreeNode(8);
const n16 = new BinaryTreeNode(16);
const n32 = new BinaryTreeNode(32);
const n64 = new BinaryTreeNode(64);
n1.setRightAndUpdateParent(n4);
n4.setLeftAndUpdateParent(n2);
n4.setRightAndUpdateParent(n16);
n16.setLeftAndUpdateParent(n8);
n16.setRightAndUpdateParent(n32);
n32.setLeftAndUpdateParent(n64);
const newParent = leftRotation(n4);
expect(newParent).toBe(n16);
expect(n8.toValues()).toMatchObject({
value: 8, left: null, right: null, parent: 4,
});
expect(n4.toValues()).toMatchObject({
value: 4, left: 2, right: 8, parent: 16,
});
});
});
describe('#rightRotation (RR Rotation)', () => {
it('should rotate single trees', () => {
// 4
// /
// 3*
// /
// 2
// /
// 1
n4.setLeftAndUpdateParent(n3);
n3.setLeftAndUpdateParent(n2);
n2.setLeftAndUpdateParent(n1);
const newParent = rightRotation(n3);
expect(newParent).toBe(n2);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: null, parent: 2,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: 1, right: 3, parent: 4,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: null, right: null, parent: 2,
});
expect(n4.toValues()).toMatchObject({
value: 4, left: 2, right: null, parent: null,
});
});
it('should right rotate at the top', () => {
// 3*
// /
// 2
// /
// 1
n3.setLeftAndUpdateParent(n2);
n2.setLeftAndUpdateParent(n1);
const newParent = rightRotation(n3);
expect(newParent).toBe(n2);
expect(n2.toValues()).toMatchObject({
value: 2, left: 1, right: 3, parent: null,
});
});
it('should RR last two', () => {
// 1
// \
// 3*
// /
// 2
n1.setRightAndUpdateParent(n3);
n3.setLeftAndUpdateParent(n2);
const newParent = rightRotation(n3);
expect(newParent).toBe(n2);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: 2, parent: null,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: null, right: 3, parent: 1,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: null, right: null, parent: 2,
});
});
it('should not lose nodes on RR', () => {
// 16* 4
// / \ / \
// 4 32 -- right-rotation(16) --> 2 16
// / \ / / \
// 2 8 1 8 32
// /
// 1
const n8 = new BinaryTreeNode(8);
const n16 = new BinaryTreeNode(16);
const n32 = new BinaryTreeNode(32);
n16.setLeftAndUpdateParent(n4);
n16.setRightAndUpdateParent(n32);
n4.setLeftAndUpdateParent(n2);
n4.setRightAndUpdateParent(n8);
n2.setLeftAndUpdateParent(n1);
const newParent = rightRotation(n16);
expect(newParent).toBe(n4);
expect(n8.toValues()).toMatchObject({
value: 8, left: null, right: null, parent: 16,
});
expect(n16.toValues()).toMatchObject({
value: 16, left: 8, right: 32, parent: 4,
});
});
});
describe('#leftRightRotation (LR Rotation)', () => {
it('should do LL rotation and RR rotation', () => {
// 4
// /
// 3*
// /
// 1
// \
// 2
n4.setLeftAndUpdateParent(n3);
n3.setLeftAndUpdateParent(n1);
n1.setRightAndUpdateParent(n2);
const newParent = leftRightRotation(n3);
expect(newParent).toBe(n2);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: null, parent: 2,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: 1, right: 3, parent: 4,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: null, right: null, parent: 2,
});
});
});
describe('#rightLeftRotation (RL Rotation)', () => {
it('should do a RR rotation and then a LL rotation', () => {
// 1*
// \
// 3
// /
// 2
n1.setRightAndUpdateParent(n3);
n3.setLeftAndUpdateParent(n2);
const newParent = rightLeftRotation(n1);
expect(newParent).toBe(n2);
expect(n1.toValues()).toMatchObject({
value: 1, left: null, right: null, parent: 2,
});
expect(n2.toValues()).toMatchObject({
value: 2, left: 1, right: 3, parent: null,
});
expect(n3.toValues()).toMatchObject({
value: 3, left: null, right: null, parent: 2,
});
});
});
});