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feat(tree): leftRightRotation
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7 files changed

+299
-21
lines changed

7 files changed

+299
-21
lines changed

‎src/data-structures/trees/avl-tree.js‎

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@@ -0,0 +1,7 @@
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const BinarySearchTree = require('./binary-search-tree');
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class AvlTree extends BinarySearchTree {
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}
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module.exports = AvlTree;

‎src/data-structures/trees/avl-tree.spec.js‎

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const AvlTree = require('./avl-tree.js');
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describe('AvlTree', () => {
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let tree;
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beforeEach(() => {
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tree = new AvlTree();
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});
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describe('#contructor', () => {
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it('should initialize', () => {
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expect(tree).not.toBe(undefined)
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});
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});
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});

‎src/data-structures/trees/red-black-tree.js‎

Lines changed: 28 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -50,8 +50,19 @@ class RedBlackTree extends BinarySearchTree {
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* @param {TreeNode} node
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*/
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balance(node) {
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// Detect RED violation
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if (node.parent && node.color === RED && node.parent.color === RED) {
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// check uncle
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if (node.uncle && node.uncle.color === RED) {
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// if uncle is RED, change the color of uncle, parent and grandparent to BLACK
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node.parent.color = BLACK;
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node.uncle.color = BLACK;
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node.grandparent.color = BLACK;
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} else if (node.uncle && node.uncle.color === BLACK) {
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// if uncle is BLACK
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// case: Right Right Case
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} else if (node.parent && node.color === RED && node.parent.color === RED) {
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// Solve RED violation doing rotations and re-color
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if (node.isParentLeftChild) {
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this.rightRotation(node.parent);
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} else {
@@ -89,14 +100,6 @@ class RedBlackTree extends BinarySearchTree {
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node.right.color = RED;
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node.left.color = RED;
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}
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// const oldParent = node.parent.clone();
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// const newParent = node.parent;
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// newParent.copy(node);
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// newParent.parent = oldParent.parent;
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// oldParent.right = undefined;
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// newParent.left = oldParent;
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}
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/**
@@ -112,14 +115,22 @@ class RedBlackTree extends BinarySearchTree {
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*
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* @param {TreeNode} node
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*/
115-
static rightRotation(node) {
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const oldParent = node.parent.clone();
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const newParent = node.parent;
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rightRotation(node) {
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const oldParent = node.parent;
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const grandParent = oldParent.parent;
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119-
newParent.copy(node);
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newParent.parent = oldParent.parent;
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oldParent.left = undefined;
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newParent.right = oldParent;
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if (grandParent) {
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// do something
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} else {
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this.root = node;
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node.parent = null;
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node.right = oldParent;
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oldParent.left = undefined;
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// re-color
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node.color = BLACK;
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node.right.color = RED;
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node.left.color = RED;
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}
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}
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}
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‎src/data-structures/trees/red-black-tree.spec.js‎

Lines changed: 48 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -46,7 +46,7 @@ describe('RedBlackTree', () => {
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expect(tree.root.left.color).toBe(RED);
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});
4848

49-
xit('should balance tree by rotating right', () => {
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it('should balance tree by rotating right', () => {
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tree.add(3);
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tree.add(2);
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tree.add(1);
@@ -56,12 +56,56 @@ describe('RedBlackTree', () => {
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1, 3,
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undefined, undefined, undefined, undefined,
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]);
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// verify colors
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expect(tree.root.color).toBe(BLACK);
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expect(tree.root.right.color).toBe(RED);
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expect(tree.root.left.color).toBe(RED);
5964
});
6065

6166
it('should change colors', () => {
62-
tree.add(1);
63-
tree.add(2);
64-
tree.add(3);
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const n1 = tree.add(1);
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const n2 = tree.add(2);
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const n3 = tree.add(3);
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const n4 = tree.add(4);
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expect(tree.toArray()).toEqual([
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2,
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1, 3,
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undefined, undefined, undefined, 4,
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undefined, undefined,
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]);
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expect(tree.root.color).toBe(BLACK);
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expect(tree.root.right.color).toBe(BLACK);
81+
expect(tree.root.left.color).toBe(BLACK);
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expect(tree.root.right.right.color).toBe(RED);
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84+
expect(n1.color).toBe(BLACK);
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expect(n2.color).toBe(BLACK);
86+
expect(n3.color).toBe(BLACK);
87+
expect(n4.color).toBe(RED);
88+
});
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90+
xtest('letf roation with grandparent', () => {
91+
const n1 = tree.add(1);
92+
const n2 = tree.add(2);
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const n3 = tree.add(3);
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const n4 = tree.add(4);
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const n5 = tree.add(5);
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expect(tree.toArray()).toEqual([
98+
2,
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1, 4,
100+
undefined, undefined, 3, 5,
101+
undefined, undefined, undefined, undefined,
102+
]);
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expect(n1.color).toBe(BLACK);
105+
expect(n2.color).toBe(BLACK);
106+
expect(n4.color).toBe(BLACK);
107+
expect(n3.color).toBe(RED);
108+
expect(n5.color).toBe(RED);
65109
});
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});
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});

‎src/data-structures/trees/tree-node.js‎

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Original file line numberDiff line numberDiff line change
@@ -87,6 +87,11 @@ class TreeNode {
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return parent.sibling;
8888
}
8989

90+
get grandparent() {
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const { parent } = this;
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return parent && parent.parent;
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}
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// Meta shortcuts
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/**

‎src/data-structures/trees/tree-rotations.js‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,51 @@
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/**
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* Single Left Rotation (LL Rotation)
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* @param {TreeNode} node
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*/
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function leftRotation(node) {
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const newParent = node.right;
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const grandparent = node.parent;
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9+
newParent.parent = node.parent;
10+
if (grandparent) { grandparent.left = newParent; }
11+
newParent.left = node;
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return newParent;
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}
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16+
/**
17+
* Single Right Rotation (RR Rotation)
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* @param {TreeNode} node
19+
*/
20+
function rightRotation(node) {
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const newParent = node.left;
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const grandparent = node.parent;
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24+
newParent.parent = node.parent;
25+
if (grandparent) { grandparent.left = newParent; }
26+
newParent.right = node;
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28+
return newParent;
29+
}
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31+
/**
32+
* Left Right Rotation (LR Rotation)
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* @param {TreeNode} node
34+
*/
35+
function leftRightRotation(node) {
36+
let newParent;
37+
newParent = leftRotation(node.left);
38+
newParent = rightRotation(node);
39+
return newParent;
40+
}
41+
42+
function rightLeftRotation(node) {
43+
44+
}
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46+
module.exports = {
47+
leftRotation,
48+
rightRotation,
49+
leftRightRotation,
50+
rightLeftRotation,
51+
};

‎src/data-structures/trees/tree-rotations.spec.js‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,145 @@
1+
const TreeNode = require('./tree-node');
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const {
3+
leftRotation,
4+
rightRotation,
5+
leftRightRotation,
6+
rightLeftRotation,
7+
} = require('./tree-rotations');
8+
9+
describe('Tree rotations', () => {
10+
let n1;
11+
let n2;
12+
let n3;
13+
let n4;
14+
let n5;
15+
16+
beforeEach(() => {
17+
n1 = new TreeNode(1);
18+
n2 = new TreeNode(2);
19+
n3 = new TreeNode(3);
20+
n4 = new TreeNode(4);
21+
});
22+
23+
describe('#leftRotation (LL Rotation)', () => {
24+
it('should rotate left with root (LL Rotation)', () => {
25+
// 1
26+
// \
27+
// 2*
28+
// \
29+
// 3
30+
// \
31+
// 4
32+
n1.right = n2;
33+
n2.right = n3;
34+
n3.right = n4;
35+
36+
const newParent = leftRotation(n2);
37+
38+
expect(newParent).toBe(n3);
39+
expect(n3.left).toBe(n2);
40+
expect(n3.right).toBe(n4);
41+
expect(n3.parent).toBe(n1);
42+
});
43+
44+
it('should rotate left with root', () => {
45+
// 1*
46+
// \
47+
// 2
48+
// \
49+
// 3
50+
// \
51+
// 4
52+
n1.right = n2;
53+
n2.right = n3;
54+
n3.right = n4;
55+
56+
const newParent = leftRotation(n1);
57+
58+
expect(newParent).toBe(n2);
59+
expect(n2.left).toBe(n1);
60+
expect(n2.right).toBe(n3);
61+
expect(n2.parent).toBe(null);
62+
});
63+
64+
it('should rotate last two', () => {
65+
// 4
66+
// /
67+
// 3
68+
// /
69+
// 1*
70+
// \
71+
// 2
72+
n4.left = n3;
73+
n3.left = n1;
74+
n1.right = n2;
75+
76+
const newParent = leftRotation(n1);
77+
expect(newParent).toBe(n2);
78+
79+
expect(n3.left.value).toBe(2);
80+
expect(n2.left.value).toBe(1);
81+
expect(n1.left).toBe(undefined);
82+
});
83+
});
84+
85+
describe('#rightRotation (RR Rotation)', () => {
86+
it('should rotate single trees', () => {
87+
// 4
88+
// /
89+
// 3*
90+
// /
91+
// 2
92+
// /
93+
// 1
94+
n4.left = n3;
95+
n3.left = n2;
96+
n2.left = n1;
97+
98+
const newParent = rightRotation(n3);
99+
100+
expect(newParent).toBe(n2);
101+
expect(n2.left).toBe(n1);
102+
expect(n2.right).toBe(n3);
103+
expect(n2.parent).toBe(n4);
104+
expect(n3.parent).toBe(n2);
105+
expect(n4.left).toBe(n2);
106+
});
107+
108+
it('should right rotate at the top', () => {
109+
// 3*
110+
// /
111+
// 2
112+
// /
113+
// 1
114+
n3.left = n2;
115+
n2.left = n1;
116+
117+
const newParent = rightRotation(n3);
118+
119+
expect(newParent).toBe(n2);
120+
});
121+
});
122+
123+
describe('#leftRightRotation (LR Rotation)', () => {
124+
it('should do LL rotation and RR rotation', () => {
125+
// 4
126+
// /
127+
// 3*
128+
// /
129+
// 1
130+
// \
131+
// 2
132+
n4.left = n3;
133+
n3.left = n1;
134+
n1.right = n2;
135+
136+
const newParent = leftRightRotation(n3);
137+
138+
expect(newParent).toBe(n2);
139+
expect(n2.left).toBe(n1);
140+
expect(n2.right).toBe(n3);
141+
expect(n2.parent).toBe(n4);
142+
expect(n4.left).toBe(n2);
143+
});
144+
});
145+
});

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