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Commit 60432d5

Browse files
adding circular list problem
1 parent 5af5e81 commit 60432d5

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3 files changed

+229
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3 files changed

+229
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‎circular/circular.js‎

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// --- Directions
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// Given a linked list, return true if the list
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// is circular, false if it is not.
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// --- Examples
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// const l = new List();
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// const a = new Node('a');
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// const b = new Node('b');
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// const c = new Node('c');
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// l.head = a;
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// a.next = b;
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// b.next = c;
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// c.next = b;
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// circular(l) // true
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// Solution
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function circular(list) {
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let slow = list.getFirst();
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let fast = list.getFirst();
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while(fast.next && fast.next.next) {
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slow = slow.next;
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fast = fast.next.next;
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if(slow === fast) {
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return true;
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}
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}
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return false;
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}

‎circular/directions.md‎

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# --- Directions
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Given a linked list, return true if the list
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is circular, false if it is not.
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# --- Examples
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const l = new List();
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const a = new Node('a');
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const b = new Node('b');
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const c = new Node('c');
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l.head = a;
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a.next = b;
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b.next = c;
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c.next = b;
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circular(l) // true
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# --- Solution
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function circular(list) {
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let slow = list.getFirst();
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let fast = list.getFirst();
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while(fast.next && fast.next.next) {
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slow = slow.next;
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fast = fast.next.next;
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if(slow === fast) {
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return true;
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}
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}
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return false;
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}

‎circular/linkedlist.js‎

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// --- Directions
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// Implement classes Node and Linked Lists
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// See 'directions' document
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class Node {
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constructor(data, next = null) {
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this.data = data;
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this.next = next;
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}
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}
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class LinkedList {
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constructor() {
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this.head = null;
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}
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insertFirst(data) {
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// this.head = new Node(data, this.head);
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this.insertAt(data,0);
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}
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size() {
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let counter = 0;
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let node = this.head;
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while(node) {
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counter++;
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node = node.next;
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}
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return counter;
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}
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getFirst() {
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// return this.head;
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return this.getAt(0);
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}
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getLast() {
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// if(!this.head) {
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// return null;
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// }
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// let node = this.head;
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// while(node) {
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// if(!node.next) {
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// return node;
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// }
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// node = node.next;
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// }
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return this.getAt(this.size()-1);
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}
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clear() {
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this.head = null;
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}
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removeFirst() {
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// if(!this.head) {
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// return;
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// }
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// this.head = this.head.next;
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this.removeAt(0);
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}
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removeLast() {
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// if(!this.head) {
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// return;
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// } else if(!this.head.next) {
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// previous = null;
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// return;
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// }
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// let previous = this.head;
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// let node = this.head.next;
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// while(node.next) {
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// previous = node;
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// node = node.next;
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// }
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// previous.next = null;
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this.removeAt(this.size()-1);
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}
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insertLast(data) {
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// if(!this.head) {
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// this.head = new Node(data);
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// } else {
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// this.getLast().next = new Node(data);
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// }
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this.insertAt(data, this.size()-1);
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}
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getAt(index) {
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let counter = 0;
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let node = this.head;
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while(node) {
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if(counter === index) {
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return node;
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}
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counter++;
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node = node.next;
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}
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return null;
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}
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removeAt(index) {
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if(!this.head) {
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return;
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}
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if(index === 0) {
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this.head = this.head.next;
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return;
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}
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const previous = this.getAt(index-1);
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if(!previous || !previous.next) {
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return;
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}
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previous.next = previous.next.next;
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}
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insertAt(data, index) {
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if(!this.head) {
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this.head = new Node(data);
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return;
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}
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if(index === 0) {
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this.head = new Node(data, this.head);
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return;
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}
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const previous = this.getAt(index-1) || this.getLast();
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const node = new Node(data, previous.next);
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previous.next = node;
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}
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forEach(fn) {
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let node = this.head;
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let counter = 0;
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while (node) {
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fn(node, counter);
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node = node.next;
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counter++;
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}
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}
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*[Symbol.iterator]() {
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let node = this.head;
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while (node) {
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yield node;
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node = node.next;
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}
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}
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}
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module.exports = { Node, LinkedList };

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