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Studying for a Tech Interview Sucks, so Here's a Cheat Sheet to Help

This list is meant to be a both a quick guide and reference for further research into these topics. It's basically a summary of that comp sci course you never took or forgot about, so there's no way it can cover everything in depth. It also will be available as a gist on Github for everyone to edit and add to.

Data Structure Basics

###Array ####Definition:

• Stores data elements based on an sequential, most commonly 0 based, index.
• Based on tuples from set theory.

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class Question {
    id: string;
    body: string;
    answer: string;
}

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interface AnswerValidationPolicy {
    isAnswerValid(userAnswer: string, correctAnswer: string): Promise<boolean>;
}

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interface NextQuestionPolicy {
    getNextQuestion(availableQuestions: Question[]): Promise<Question>;
}

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interface QuestionRepository {
    getAvailableQuestions(categoryId: string): Promise<Question[]>;
    getById(questionId: string): Promise<Question>;
}

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...
export function getQuestions(categoryId: string): Promise<{ id: string, question: string, answer: string}[]>
export function getQuestion(questionId: string): Promise<{ id: string, question: string, answer: string}>
...

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import { getQuestions, getQuestion } from '../../../question-store';

export default class QuestionStoreRepository implements QuestionRepository {
    async getAvailableQuestions(categoryId: string): Promise<Question[]> {
        const rawQuestions = await getQuestions(categoryId);
        return rawQuestions.map(rawQuestion => new Question(
            rawQuestion.id,
            rawQuestion.question,
            rawQuestion.answer
        ));

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class RandomNextQuestionPolicy implements NextQuestionPolicy {
    async getNextQuestion(availableQuestions: Question[]): Promise<Question> {
        if (availableQuestions.length === 0) 
            throw new Error('Next question is not available');
        
        const nextRandomIndex = RandomNextQuestionPolicy.getRandomInt(
            0, availableQuestions.length - 1
        );
        return Promise.resolve(availableQuestions[nextRandomIndex]);
    }

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class TextEqualityAnswerValidationPolicy implements AnswerValidationPolicy {
    isAnswerValid(userAnswer: string, correctAnswer: string): Promise<boolean> {
        return Promise.resolve(
            userAnswer.trim().toLowerCase() === correctAnswer.toLowerCase()
        );
    }
}

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class AnswerResult {
    userAnswer: string;
    isValid: boolean;
    correctAnswer: string;
}

class AnswerQuestion {
    questionRepository: QuestionRepository;
    answerValidationPolicy: AnswerValidationPolicy;