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ashokdeyashokdey
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Merge branch 'master' into DoublyLinkList
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‎README.md

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@@ -14,20 +14,29 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
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### Data Structures
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- [Singly Linked List](src/_DataStructures_/LinkedList)
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- [N Element From Last](src/_DataStructures_/LinkedList/element-from-last)
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- [Middle Node](src/_DataStructures_/LinkedList/middle-node)
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- [Detect Loop](src/_DataStructures_/LinkedList/loop-in-list)
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- [Reverse Linked List](src/_DataStructures_/LinkedList/reverse-linked-list)
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- [Stack](src/_DataStructures_/Stack)
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- [Implement Queue Using Stack](src/_DataStructures_/Stack/immitate-queue-using-stack)
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- [Baseball Game](src/_DataStructures_/Stack/baseball-game)
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- [Minimum Stack](src/_DataStructures_/Stack/min-stack)
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- [Balanced Parenthesis](src/_DataStructures_/Stack/balanced-parenthesis)
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- [Postfix Expression Evaluation](src/_DataStructures_/Stack/postfix-expression-evaluation)
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- [Remove Consecutive Repeated Digits](src/_DataStructures_/Stack/remove-consecutive-repeated-digits)
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- [Implement 2 Stacks using Single Array](src/_DataStructures_/Stack/2-stacks-using1-array)
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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)
@@ -41,6 +50,7 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
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- [Get Maze Path](src/_Problems_/get_subsequence)
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- [Get longest consecutive 1s](src/_Problems_/max-consecutive-1s)
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- [Get Max Char](src/_Problems_/maxchar)
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- [Get Smallest Common Number](src/_Problems_/get-smallest-common-number)
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- [Merge 2 Sorted Arrays](src/_Problems_/merge-two-sorted-arrays)
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- [Palindrome](src/_Problems_/palindrome)
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- [Product of Elements](src/_Problems_/product-of-elements)
@@ -66,3 +76,25 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
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- [Caeser Cipher](src/_Classics_/caeser_cipher)
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- [Fibonacci](src/_Classics_/fibonacci)
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---
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## CONTRIBUTION Guide
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It's great to know that you want to contribute to this repo. Thanks for taking interest. Before you start, read the following carefully.
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- When adding a new **problem** with solution
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- Take care of the filename convention (Very Important)
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- Problem statement should be there with examples
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- Make sure you add the Run Time complexity of your solution
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- Please take care of the segregation of the Problems as per the given Folder Structure
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- It's great if you can add the **Unit Tests** to verify your solutions as well
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- Strictly follow ESLINT rules
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- When adding a Unit Test
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- Take care of the file name convention
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- Make sure CI (Travis) is passing
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Keep an eye on this guide, it's subjected to change frequently.

‎src/_Classics_/fibonacci/index.js

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@@ -1,9 +1,11 @@
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//The Fibonacci sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21
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// the algorithm has time complexity of O(n^2), very bad!
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function fibonacci(position) {
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// if position is 1 or 2, the number in fibonacci sequence will be 1
4-
if (position < 3) {
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return 1;
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if (position <= 1) {
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return position;
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}
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// else the element in fibonacci sequence will be the sum of
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// element at position(p) (p -1) and (p - 2)
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return fibonacci(position - 2) + fibonacci(position - 1);
@@ -24,8 +26,8 @@ function fibonacciMemoized(index, cache) {
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if (cache[index]) {
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return cache[index];
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} else {
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if (index < 3) {
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return 1;
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if (index <=1) {
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return index;
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} else {
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cache[index] =
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fibonacciMemoized(index - 1, cache) +
@@ -41,7 +43,9 @@ function fibonacciMemoized(index, cache) {
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function fibonacciTabular(n) {
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const table = [0, 1];
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if (n <= 1) {
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return n;
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}
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for (let i = 2; i <= n; i += 1) {
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table[i] = table[i - 1] + table[i - 2];
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}
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// console.log(`Fib normal - ${fibonacci(number)}`);
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// console.log('--');
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// console.log(`Fib memo - ${fibonacciMemoized(number)}`);
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// console.log(`Fib table - ${fibonacciTabular(number)}`);
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// console.log(`Fib table - ${fibonacciTabular(number)}`);

‎src/_DataStructures_/LinkedList/loop-in-list/index.js

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// Floyd’s Cycle-Finding Algorithm
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function detechLoop(linkedList) {
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function detectLoop(linkedList) {
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let slow = linkedList.getFirst();
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let fast = linkedList.getFirst();
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@@ -14,3 +14,7 @@ function detechLoop(linkedList) {
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}
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return false;
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}
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module.exports = {
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detectLoop,
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};

‎src/_DataStructures_/LinkedList/loop-in-list/loop-in-list.test.js

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const { LinkedList } = require('../index');
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const { detectLoop } = require('.');
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describe('Loop a LinkedList', () => {
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let loopList = null;
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let last = null;
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beforeEach(() => {
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loopList = new LinkedList();
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loopList.addAtBeginning('1');
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loopList.addAtEnd('2');
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loopList.addAtEnd('3');
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loopList.addAtEnd('4');
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loopList.addAtEnd('5');
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// Create loop in list
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last = loopList.getLast();
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last.next = loopList.getFirst();
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});
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it('Should break for empty list', () => {
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loopList.delete();
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expect(() => detectLoop(loopList)).toThrow(TypeError);
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});
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it('Should return `true` when looping list', () => {
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expect(detectLoop(loopList)).toEqual(true);
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});
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it('Should return `false` for non loop list', () => {
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last.next = null; // remove loop in list
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expect(detectLoop(loopList)).toEqual(false);
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});
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it('Should return `false` for non loop list', () => {
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const list = new LinkedList();
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list.addAtBeginning('1');
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list.addAtEnd('1');
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list.addAtEnd('1');
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expect(detectLoop(list)).toEqual(false);
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});
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});

‎src/_DataStructures_/Stack/2-stacks-using1-array/index.js

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/**
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* Revision to PR #35 where I implemented bullshit thinking of
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* new breakthrough :D
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*/
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class TwoStacks {
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constructor(capacity) {
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this.data = [];
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this.top1 = -1;
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this.top2 = capacity;
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this.overflow = new Error('Overflow: Stack is full');
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this.capacity = capacity;
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}
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push1(value) {
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if (this.top1 < this.top2 - 1) {
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this.top1 += 1;
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this.data[this.top1] = value;
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} else {
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throw this.overflow;
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}
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}
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push2(value) {
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if (this.top1 < this.top2 - 1) {
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this.top2 -= 1;
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this.data[this.top2] = value;
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} else {
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throw this.overflow;
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}
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}
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pop1() {
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if (this.top1 >= 0) {
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const item = this.data[this.top1];
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delete this.data[this.top1];
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this.top1 -= 1;
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return item;
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}
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return -1;
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}
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pop2() {
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if (this.top2 < this.capacity) {
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const item = this.data[this.top2];
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delete this.data[this.top2];
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this.top2 += 1;
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return item;
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}
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return -1;
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}
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}
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module.exports = TwoStacks;
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/** Test cases */
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/*
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const s = new TwoStacks(4);
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s.push1('a');
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console.log(s.data);
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s.push2('a2');
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console.log(s.data);
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s.push1('b');
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console.log(s.data);
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s.push2('b2');
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console.log(s.data);
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s.push2('d2');
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console.log(s.data);
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s.push2('c23');
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console.log(s.data);
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console.log(s.pop2());
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console.log(s.data);
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console.log(s.pop1());
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console.log(s.data);
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*/

‎src/_DataStructures_/Stack/postfix-expression-evaluation/index.js

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/**
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* Evaluation of Postfix Expression
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* Input:456*+
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* Output:34
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*/
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const Stack = require('../index');
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function evaluatePostfixExpression(expression) {
10+
let s = new Stack();
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for (let i = 0; i < expression.length; i++) {
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const char = expression[i];
13+
if (!isNaN(char)) {
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//if number push the char onto stack
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s.push(Number(char));
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} else {
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// if char is an operator then pop two elements from stack, evaluate them accordingly based on operator.
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//push the result to stack
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let val1 = s.pop();
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let val2 = s.pop()
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switch (char) {
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case '+':
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s.push(val2 + val1);
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break;
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case '-':
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s.push(val2 - val1);
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break;
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case '*':
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s.push(val2 * val1);
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break;
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case '/':
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s.push(val2 / val1);
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break;
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}
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}
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}
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//pop the value of postfix expression
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return s.pop();
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}

‎src/_DataStructures_/Stack/remove-consecutive-repeated-digits/index.js

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/**
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* Given an integer N, remove consecutive repeated digits from it.
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* Input:133445
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* Output:1345
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*/
6+
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const Stack = require('../index');
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9+
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function removeConsecutiveDigits(no) {
11+
let s = new Stack();
12+
let newNo = "";
13+
//initally push first digit into stack
14+
newNo += no[0];
15+
s.push(no[0]);
16+
for (let i = 1; i < no.length; i++) {
17+
const digit = no[i];
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//if stack top and incoming digit is same ignore it else append to newNo.
19+
if (s.peek() !== digit) {
20+
newNo += digit;
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s.push(digit);
22+
}
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}
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return newNo
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}

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