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Data Structures & Algorithms

Given a json string with nested objects, write a function that flattens all the objects to a single key-value dictionary.

Flatten JSON

Write a function to sum two numeric strings without converting them to integers and return the result as a string

Summing Numeric Strings

Write a class 'SinglyLinkedList' that implements the interface required for a Singly Linked List.

Singly Linked List

Machine Learning

Bias vs. Variance Tradeoff

Let's say that you're training a classification model.   How would you combat overfitting when building tree-based models?

Overfit Avoidance

Explain what backpropagation does, its informal intuition, drawbacks, and derive/prove it

Backpropagation Explanation

Behavioral

How would you answer when an Interviewer asks why you applied to their company?

Why Do You Want to Work With Us

What do you tell an interviewer when they ask you what your strengths and weaknesses are?

Your Strengths and Weaknesses

Design Patterns

Create a text editor while displaying method overriding as a concept.

Text Editor With OOP

DevOps

Design a cloud-agnostic CI/CD pipeline supporting safe deployments and rollbacks across multiple providers.

Cloud-Agnostic Deployments

Given a <code>JSON</code> string with nested objects, write a function <code>flatten_json</code> that flattens all the objects to a single key-value dictionary. Do not use the library that actually performs this function.

Example:

Input:

<pre tabindex="0" class="chroma"><code>import json
json_str = json.dumps({&#39;a&#39;:{&#39;b&#39;:&#39;c&#39;, &#39;d&#39;:&#39;e&#39;}})
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def flatten_json(json_str) -&gt; json.dumps({&#39;a_b&#39;:&#39;c&#39;, &#39;a_d&#39;:&#39;e&#39;})
</code></pre>

Note: Input and output are in <code>string</code> format : use <code>json.dumps()</code> to convert python dictionary to string.

Imagine you are asked to build a machine learning model to decide new loan approvals for a
financial firm. You ask the data department in the company for a subset of data to get started
working on the problem. The data includes different features about applicants such as age,
occupation, zip code, height, number of children, favorite color, etc. You decide to build
multiple machine learning models to test out different ideas before settling on the best one.

How would you explain the bias-variance tradeoff with regards to
building and choosing a model to use?

Let’s say you’re a data engineer at Fidelity Investments, and you’re running a SQL query on a cloud-based data warehouse. All cluster resources and network health metrics look normal, but the query is still taking over 10 minutes to complete.

How would you go about diagnosing and improving the performance of this query?

How would you diagnose and speed up a slow SQL query when system metrics look healthy?

Slow SQL Query

Query Optimization

Let’s say that you’re training a classification model.

How would you combat overfitting when building tree-based models?

When an interviewer asks a question along the lines of:

<ul>
<li>What would your current manager say about you? What constructive criticisms might he give?</li>
<li>What are your three biggest strengths and weaknesses you have identified in yourself?</li>
</ul>

How would you respond?

When asked about your strengths in an interview, what is an effective way to respond?

When asked about your strengths in an interview, what is an effective way to respond?

Your Strengths and Weaknesses I

Which of the following is an acceptable strategy when discussing weaknesses in an interview?

Which of the following is an acceptable strategy when discussing weaknesses in an interview?

Your Strengths and Weaknesses II

Given two strings, <code>num_str1</code> and <code>num_str2</code>, write a function to sum the two strings together without directly converting them to integers.

Note: Return the output in string format.

Example:

Input:

<pre tabindex="0" class="chroma"><code>num_ str1 = &#39;122&#39; #assume that in practice the two strings are huge
num_str2 = &#39;222&#39;
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>sum_strings(num_str1,num_str2) -&gt; &#39;344&#39;
</code></pre>

You have been tasked with designing three classes: <code>text_editor</code>, <code>moving_text_editor</code>, and <code>smart_text_editor</code>. These classes are to be created with specific functionalities as defined below:

<ol>
<li><code>text_editor</code> class:

<ul>
<li><code>write_line(string:str)</code>: A method which appends a given string to the end of the existing string.</li>
<li><code>delete_line(char_num : int)</code>: A method which deletes <code>char_num</code> number of characters from the existing string, starting from the end. If there are no characters left, the method should do nothing.</li>
<li><code>special_operation()</code>: A method which currently does nothing.</li>
<li><code>get_notes()</code>: A method which returns the internal string.</li>
</ul></li>

<li><code>moving_text_editor</code> class:

<ul>
<li>This class extends <code>text_editor</code>. The <code>special_operation()</code> method is overridden. Initially, the cursor will be at the end of the current string. If <code>special_operation()</code> is called, it moves the cursor to the beginning of the string, any additional appends will be appended to the beginning of the string instead. Calling <code>special_operation()</code> again reverses the cursor operation.</li>
</ul></li>

<li><code>smart_text_editor</code> class:

<ul>
<li>This class extends <code>text_editor</code>. In this class, the <code>special_operation()</code> method is overridden to serve as an undo operation, allowing it to undo an infinite number of operations.</li>
</ul></li>
</ol>

<h3>Input</h3>

<pre tabindex="0" class="chroma"><code>[[&#39;special_text_editor&#39;], [&#39;write_line&#39;, &#39;special_operation&#39;, &#39;write_line&#39;], [&#39;World&#39;, &#39;Hello, &#39;]]
</code></pre>

<h3>Output</h3>

<code>&#34;Hello, World&#34;</code>

You work as a DevOps engineer for a global SaaS company with services deployed across multiple cloud providers. The team wants to implement a cloud-agnostic CI/CD pipeline that supports safe, zero-downtime deployments for critical microservices. The deployment process should allow for rapid rollback, controlled traffic shifting, and minimal service disruption.

How would you design this CI/CD and deployment system?

When an interviewer asks you a question along the lines of:

<ul>
<li>Why did you apply to our company?</li>
<li>What are you looking for in your next job?</li>
<li>What makes you a good fit for our company?</li>
</ul>

How should you respond?

When asked 'What are you looking for in your next job?' in an interview, how can you tie the company's employee benefits into your response?

When asked 'What are you looking for in your next job?' in an interview, how can you tie the company's employee benefits into your response?

Why Do You Want to Work With Us I

How can company values be used effectively in an interview when asked 'What makes you a good fit for our company?'

How can company values be used effectively in an interview when asked 'What makes you a good fit for our company?'

Why Do You Want to Work With Us II

When responding to the question 'Why did you apply to our company?' during an interview, what aspect should you highlight?

When responding to the question 'Why did you apply to our company?' during an interview, what aspect should you highlight?

Why Do You Want to Work With Us III

Let’s say a lottery-winning donor wants to open a network of kindergartens in her rural Turkish hometown, aiming to make them affordable for local families and self-sustaining after her initial investment. She hired you as a Business Analyst consultant to lead the strategy for her mission.

How would you approach evaluating the feasibility of this plan, and what key factors or analyses would you consider to ensure both affordability and long-term sustainability?

How would you as a consultant develop a strategy for a client's mission of building an affordable, self-sustaining kindergartens in a rural Turkish town?

Kindergarten Feasibility

Estimation

Let’s say we want to launch a re-design of a landing page to improve the click-through rate. We can do this by implementing an AB test.
Given that we launch an AB test, how would you infer if the results of the click-through rate were statistically significant or not?

How can you accurately conclude if the results of an A/B test, conducted to evaluate the effectiveness of a landing page redesign, are statistically significant?

How can you accurately conclude if the results of an A/B test, conducted to evaluate the effectiveness of a landing page redesign, are statistically significant?

Statistically Significant Test

Precisely ascertain whether the outcomes of an A/B test, executed to assess the impact of a landing page redesign, exhibit statistical significance.

A/B Testing

Singly-linked lists are a type of linked list where nodes have only one pointer: A pointer to the next element. Create a class <code>SinglyLinkedList</code> along with its methods:

<ul>
<li><code>add_head(element)</code> - adds an element to the head of the list. This becomes the new head of the linked list.</li>
<li><code>add_tail(element)</code> - adds an element to the tail of the list. This becomes the new tail of the linked list.</li>
<li><code>remove_head() -&gt; element</code> - removes the head and returns the value of the removed element.</li>
<li><code>remove_tail() -&gt; element</code> - removes the tail and returns the value of the removed element.</li>
<li><code>__contains__(item) -&gt; bool</code> - checks if the item is inside the list. Returns <code>True</code> if it is inside the list and returns <code>False</code> if not. This method is implemented to allow the use of Python’s <code>in</code> operator.</li>
<li><code>__getitem__(index)</code> - returns the element at the specified index. Raises an <code>IndexError</code> if the index is out of bounds. This method is implemented to allow the use of Python’s <code>[]</code> operator.</li>
<li><code>__len__()</code> - returns the length of the <code>SinglyLinkedList</code>.</li>
</ul>

What does the backpropagation algorithm do in the context of neural networks? What is the informal intuition behind the algorithm? What are some drawbacks of the algorithm compared to other optimization methods?

Bonus: Formally derive the backpropagation algorithm and prove that it does what it claims to do.

Calculate Moving Average	SQL	Easy
Predict Customer Churn	Machine Learning	Medium
A/B Test Significance	Statistics	Medium
Optimize Query Performance	SQL	Hard
Feature Importance Analysis	Machine Learning	Medium
Clean Missing Data	Python	Easy
Neural Network Architecture	Deep Learning	Hard
Calculate Cohort Retention	SQL	Medium
Bayesian Probability	Statistics	Easy
Recommend Similar Products	Machine Learning	Hard

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