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Commit 65538e2

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Merge pull request #32 from knaxus/DoublyLinkList
doubly link list
2 parents 25c7a15 + 1789caf commit 65538e2

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3 files changed

+142
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‎README.md

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@@ -34,9 +34,9 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
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- [Queue](src/_DataStructures_/Queue)
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- [Weave](src/_DataStructures_/Queue/weave)
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- [Doubly Linked List](src/_DataStructures_/DoublyLinkedList)
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- [Suffix Tree](src/_DataStructures_/SuffixTree)
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### Logical Problems
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- [Anagrams](src/_Problems_/anagrams)
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- [Binary Search](src/_Searching_/BinarySearch)
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### Algorithms
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- [LRU Cache](src/_Algorithms_/lru-cache)
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### Path Finder
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- [A\*](src/PathFinder/AStart)

‎src/_Algorithms_/lru-cache/index.js

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/*
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Least recently used (LRU) - cache implementation
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get(key) – Get the value (will always be positive) of the key if the key exists in the cache, otherwise return false.
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Complexity: O(1)
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set(key, value) – Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.
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Complexity: O(1)
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*/
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const DoublyLinkedList = require('../../_DataStructures_/DoublyLinkedList/index');
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class LRUCache {
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constructor(n) {
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this.size = n;
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this.map = new Map();
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this.list = new DoublyLinkedList();
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}
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// this method will work in O(1)
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set(key, value) {
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const data = {
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key,
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value,
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};
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if (!this.map.has(key)) {
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this.list.addAtBeginning(data);
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this.map.set(key, this.list.head.next);
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if (this.list.length() > this.size) {
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const lastNode = this.list.tail.previous.data;
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this.map.delete(lastNode.key);
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this.list.removeAtEnd();
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}
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} else {
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this.list.remove(this.map.get(key));
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this.list.addAtBeginning(data);
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this.map.set(key, this.list.head.next);
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}
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}
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// this method will work in O(1)
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get(key) {
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if (this.map.has(key)) {
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const node = this.map.get(key);
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const { value } = node.data;
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this.list.remove(node);
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this.list.addAtBeginning({
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key,
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value,
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});
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this.map.set(key, this.list.head.next);
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}
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return false;
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}
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}
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// const lru = new LRUCache(3);
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// lru.set(1, 1);
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// lru.set(2, 2);
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// lru.set(3, 3);
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// lru.set(4, 4);
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// lru.set(5, 5);
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// lru.set(2, 2);
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// lru.get(5, 5);
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// lru.list.display();
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module.exports = {
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LRUCache,
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};
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/* eslint-disable class-methods-use-this */
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class Node {
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constructor(data, previous, next) {
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this.data = data;
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this.previous = previous;
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this.next = next;
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}
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}
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class DoublyLinkedList {
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constructor() {
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// head -> tail
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// head <- tail
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this.head = new Node(null, null, null);
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this.tail = new Node(null, null, null);
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this.head.next = this.tail; // head next point to tail
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this.tail.previous = this.head; // tail previous point to head
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this.size = 0;
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}
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addAtBeginning(value) {
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const newNode = new Node(value, this.head, this.head.next);
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this.head.next.previous = newNode;
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this.head.next = newNode;
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this.size += 1;
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}
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addAtEnd(value) {
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const newNode = new Node(value, this.tail.previous, this.tail);
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this.tail.previous.next = newNode;
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this.tail.previous = newNode;
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this.size += 1;
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}
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removeAtBeginning() {
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this.remove(this.head.next);
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this.size -= 1;
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}
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removeAtEnd() {
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this.remove(this.tail.previous);
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this.size -= 1;
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}
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remove(node) {
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const previousNode = node.previous;
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const nextNode = node.next;
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previousNode.next = nextNode;
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nextNode.previous = previousNode;
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}
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length() {
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return this.size;
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}
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display() {
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let address = this.head.next;
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while (address !== this.tail) {
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console.log(address.data);
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address = address.next;
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}
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}
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}
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module.exports = DoublyLinkedList;

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