Prepare for and practice interview questions from Brightspeed.

Brightspeed Interview Questions

Brightspeed Interview Guides

Data Structures & Algorithms

Given two sorted lists, write a function to merge them into one sorted list.

Merge Sorted Lists

Find the missing integer from a array of consequtive integers

Find the Missing Number

Write a function n_frequent_words that returns the top N frequent words and their frequencies, and state its run-time

Get Top N Frequent Words

Given an integer N, write a function that returns all of the prime numbers up to N

Prime to N

Write a function is_subsequence to find out if string1 is a subsequence of string2

String Subsequence

Machine Learning

Lasso vs Ridge

In which case would you use a bagging algorithm versus a boosting algorithm

Bagging vs Boosting

How would you build the recommendation algorithm for type-ahead search for Netflix

Type-ahead Search

What metrics would you use to track accuracy and validity of the model

Spam Classifier 

How would you evaluate whether a decision tree is the right model and assess its performance before and after deployment

Decision Tree Evaluation

Select the 2nd highest salary in the engineering department

2nd Highest Salary

7 Day Streak

Find the average yearly purchases for each product

Average Quantity

Write a query to get the top five projects by budget-to-employee-count ratio

Employee Project Budgets

Payments Received

Behavioral

Describing a data project and its challenges

Hurdles In Data Projects

Strategically resolving misaligned expectations with stakeholders for a successful project outcome

Stakeholder Communication

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

Why Do You Want to Work With Us

How would you negotiate and resolve disagreements when a client rejects your proposed solution?

Client Solution Pushback

Making data-driven insights actionable for those without technical expertise

Simple Explanations

Product Sense & Metrics

Google Maps Improvement

Let's say that we want to improve the "search" feature on the Facebook app.

Improve Search Results

The role of A/B testing in measuring the success rate of an analytics experiment

Success Measurement

Classify companies as resilient, localized, or systemic stock-out risk, then propose three falsifiable hypotheses explaining the distribution

Out of Stock Inventory

How would you determine if high off-peak data usage is fraud or abuse, and what would you do about it?

Unlimited Plan Abuse

Write a SQL query to select the 2nd highest salary in the engineering department.

Note: If more than one person shares the highest salary, the query should select the next highest salary.

Example:

Input:

<code>employees</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<code>departments</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>

Given an integer <code>N</code>, write a function that returns a list of all of the prime numbers up to <code>N</code>.

Note: Return an empty list there are no prime numbers less than or equal to <code>N</code>.

Example:

Input:

<pre tabindex="0" class="chroma"><code>N = 3
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def prime_numbers(N) -&gt; [2,3]
</code></pre>

Given two sorted lists, write a function to merge them into one sorted list.

Bonus: What’s the time complexity?

Example:

Input:

<pre tabindex="0" class="chroma"><code>list1 = [1,2,5]
list2 = [2,4,6]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def merge_list(list1,list2) -&gt; [1,2,2,4,5,6]
</code></pre>

You have two sorted lists, one with m elements and one with n elements. What would be the time complexity of merging the two lists via merge sort?

You have two sorted lists, one with m elements and one with n elements. What would be the time complexity of merging the two lists via merge sort? 

Merging Lists Complexity

Tell me about a data project that didn’t go the way you expected. What did you set out to do, what surprised you, and how did you handle it?

Given a table of <code>transactions</code>, write a query to find the average quantity of each product purchased per transaction each year.

The output should include the year, product_id, and average quantity of the product purchased per transaction that year. The output table should be sorted by year and product_id in ascending order. The value for avg_quantity should be rounded to two decimal places.

Example:

Input:
<code>transactions</code> table

<table>
<thead>
<tr>
<th>Columns</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>product_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>quantity</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Columns</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>year</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>product_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>avg_quantity</code></td>
<td>DECIMAL</td>
</tr>
</tbody>
</table>

Let’s say we’re comparing two machine learning algorithms. In which case would you use a bagging algorithm versus a boosting algorithm? 

Give an example of the tradeoffs between the two.

In machine learning, when would you use a bagging algorithm over a boosting algorithm?

In machine learning, when would you use a bagging algorithm over a boosting algorithm?

Bagging vs. Boosting

Let’s say you work at Allstate. Allstate is running <code>N</code> online ads right now. The table <code>ads</code> contains all those ads, ranked by popularity via the <code>id</code> column (e.g., the entry with <code>id = 1</code> is the most popular, etc.).

Create a subquery or common table expression named <code>top_ads</code> containing the top 3 ads (by popularity) and return the number of rows that would result from the following operations

<ol>
<li><code>ads INNER JOIN top_ads</code></li>
<li><code>ads LEFT JOIN top_ads</code></li>
<li><code>ads RIGHT JOIN top_ads</code></li>
<li><code>ads CROSS JOIN top_ads</code></li>
</ol>

Note: Please make the <code>join_type</code> column in your output have the values <code>inner_join</code>, <code>left_join</code>, etc. for each of their respective join types

Note: Please return only one query with each number in a different row

Example:

Input:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>join_type</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>number_of_rows</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>

Create top_ads with the top 3 ads and return the row counts for inner, left, right, and cross joins with ads

Size of Joins

Over budget on a project is defined when the salaries, prorated to the day, exceed the budget of the project.

For example, if Alice and Bob both combined income make 200K and work on a project of a budget of 50K that takes half a year, then the project is over budget given 0.5 * 200K = 100K &gt; 50K.

Write a query to forecast the budget for all projects and return a label of <code>&#34;overbudget&#34;</code> if it is over budget and <code>&#34;within budget&#34;</code> otherwise.

Note: Assume that employees only work on one project at a time.

Example:

Input:

<code>employees</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<code>projects</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>title</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>state_date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>end_date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>budget</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
departments table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<code>employee_projects</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>project_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>employee_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>title</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>project_forecast</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>

Write a query to forecast each project's budget and label it overbudget or within budget

Over-Budget Projects

You have an array of integers, <code>nums</code> of length <code>n</code> spanning <code>0</code> to <code>n</code> with one missing. Write a function <code>missing_number</code> that returns the missing number in the array.

Note: Complexity of $O(n)$ required.

Example:

Input:

<pre tabindex="0" class="chroma"><code>nums = [0,1,2,4,5] 
missing_number(nums) -&gt; 3
</code></pre>

You’re given a string that may contain the characters <code>{</code>, <code>}</code>, <code>[</code>, <code>]</code>, <code>(</code>, and <code>)</code>.

Task: Verify that the string is balanced. A balanced string is one where every opening character, <code>{</code>, <code>[</code>, or <code>(</code>, has a corresponding closing character, <code>}</code>, <code>]</code>, or <code>)</code>.

Write a function called <code>is_balanced(string: str) -&gt; bool</code> which verifies the balance of a string.

Example:

<pre tabindex="0" class="chroma"><code>is_balanced(&#39;(())[]{}&#39;) -&gt; True
</code></pre>

<pre tabindex="0" class="chroma"><code>is_balanced(&#39;{([(){}])()}&#39;) -&gt; True
</code></pre>

<pre tabindex="0" class="chroma"><code>is_balanced(&#39;{}[]())&#39;) -&gt; False
</code></pre>

<hr/>

Write a function that tests whether a string of brackets is balanced.

The Brackets Problem

Given a table of account statuses, write a query to get the percentage of accounts that were active on December 31st, 2019, and closed on January 1st, 2020, over the total number of accounts that were active on December 31st.
Each account has only one daily record indicating its status at the end of the day.

Note: Round the result to 2 decimal places.

Example:

Input:

<code>account_status</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>account_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>status</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>

<table>
<thead>
<tr>
<th>account_id</th>
<th>date</th>
<th>status</th>
</tr>
</thead>

<tbody>
<tr>
<td>1</td>
<td>2020-01-01</td>
<td>closed</td>
</tr>

<tr>
<td>1</td>
<td>2019-12-31</td>
<td>open</td>
</tr>

<tr>
<td>2</td>
<td>2020-01-01</td>
<td>closed</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>percentage_closed</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>

Write a query to get the percentage of accounts active on December 31st, 2019 and closed on January 1st, 2020 over accounts active on December 31st, rounded to 2 decimals

Closed Accounts

How would you explain what a p-value is to someone who is not technical?

What does a p-value in a statistical test represent?

What does a p-value in a statistical test represent?

P-value to a Layman I

In a statistical test, how does a low p-value (less than 0.05) influence our decision about the null hypothesis?

In a statistical test, how does a low p-value (less than 0.05) influence our decision about the null hypothesis?

P-value to a Layman II

Explain what a p-value is to someone who is not technical

P-value to a Layman

Statistics

You are tasked with keeping track of a customer’s addresses in your database.

However, customer’s addresses change whenever they move. We want to keep track of their moving history as well as the person that moves in afterwards.

How would you create or modify a schema to keep track of these address changes?

Create a schema to keep track of customer address changes

Address Schema

Data Modeling

We’re given two tables. One is named <code>projects</code> and the other maps employees to the projects they’re working on.

Write a query to get the top five most expensive projects by budget to employee count ratio.

Note: Exclude projects with 0 employees. Assume each employee works on only one project.

<code>projects</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>title</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>state_date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>end_date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>budget</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<code>employee_projects</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>project_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>employee_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>title</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>budget_per_employee</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>

Let’s say that you’re the PM on Google Maps.

<ol>
<li>How would you improve Google Maps?</li>

<li>What metrics would you check to see if your feature improvements are successful?</li>
</ol>

Given a list of strings, write a function, <code>sorting</code> from scratch to sort the list in ascending alphabetical order.

Notes:
- Do NOT use the built-in <code>sorted</code> function
- Return the new sorted list, rather than modifying the list in-place

Bonus: Have your solution be $O(n log(n))$.

Example:

Input:

<pre tabindex="0" class="chroma"><code>array = [&#34;apple&#34;, &#34;cat&#34;, &#34;banana&#34;, &#34;zoo&#34;, &#34;football&#34;]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def sorting(array) -&gt; [&#34;apple&#34;, &#34;banana&#34;, &#34;cat&#34;, &#34;football&#34;, &#34;zoo&#34;]
</code></pre>

Write a function `sorting` from scratch to sort a list of strings in ascending alphabetical order

Sort Strings

Given a list of integers, find the index at which the sum of the left half of the list is equal to the right half. If there is no index where this condition is satisfied return -1.

Note: the number that lies on the index is calculated to the left side of the list.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>nums = [1, 7, 3, 5, 6]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>equivalent_index(nums) -&gt; 2
</code></pre>

In this example, the sum of the elements to the left of index 2 (1 + 7) is equal to the sum of the elements to the right of index 2 (5 + 6).

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>nums = [1,3,5]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>equivalent_index(nums) -&gt; -1
</code></pre>

In this example, there is no index where the sum of the elements to the left is equal to the sum of the elements to the right.

The task is to write a function that takes a list of integers as input and returns the index at which the sum of the integers to the left of the index is equal to the sum of the integers to the right. If no such index exists, the function should return -1.

Find the Index with Equal Left and Right Sum

Given a <code>ListNode</code> representing the head of a linked list, write a function <code>is_cyclic</code> which returns <code>True</code> if a linked list is cyclic and <code>False</code> if it is not. A linked list is cyclic when there is no tail to the linked list, and the supposed tail is attached to another node inside the list itself, creating a cycle.

A <code>ListNode</code> is defined as:

<pre tabindex="0" class="chroma"><code>class ListNode:
	value: ListNode = None
 next: ListNode = None
</code></pre>

Example:

Input:

<img src="/s3/questions/1a65651d-a483-4481-b073-2738d65ab9d7.png" alt="image"/>

Output:

<pre tabindex="0" class="chroma"><code>def is_cyclic(head) -&gt; True
</code></pre>

Cyclic Detection

Given two strings, <code>string1</code> and <code>string2</code>, write a function <code>is_subsequence</code> to find out if <code>string1</code> is a subsequence of <code>string2</code>.

Bonus: A subsequence is a sequence that can be derived from another sequence by deleting some elements without changing the order of the remaining elements.

Example:

Input:

<pre tabindex="0" class="chroma"><code>string1 = &#39;abc&#39;
string2 = &#39;asbsc&#39;
string3 = &#39;acedb&#39;

is_subsequence(string1, string2) -&gt; True
is_subsequence(string1, string3) -&gt; False
</code></pre>

<ol>
<li>Given an example paragraph string and an integer <code>N</code>, write a function <code>n_frequent_words</code> that returns the top <code>N</code> frequent words in the posting and the frequencies for each word.</li>

<li>What’s the function run-time?</li>
</ol>

Example:

Input:

<pre tabindex="0" class="chroma"><code>posting = &#34;&#34;&#34;
Herbal sauna uses the healing properties of herbs in combination with distilled water. 
The water evaporates and distributes the effect of the herbs throughout the room. 
A visit to the herbal sauna can cause real miracles, especially for colds. 
&#34;&#34;&#34; 
n = 3
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>n_frequent_words(posting,N) = [
 (&#39;the&#39;, 6), 
 (&#39;herbal&#39;, 2), 
 (&#39;sauna&#39;, 2),
]
</code></pre>

Let’s say Verizon launches a wireless plan that offers unlimited data after 8 p.m. each night, and you notice some customers suddenly using 10x more data during that window than the average user.

How would you distinguish between fraud and product abuse in this scenario, and how might your findings shape future product or policy decisions?

Using the <code>employees</code> table, get the total salary of all employees.

Example:

Input:

<code>employees</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>manager_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>total_salary</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>

Total Salary

Given a string <code>sentence</code>, return the same string with an addendum after each character of the number of occurrences a character appeared in the <code>sentence</code>.

Note: don’t treat the spaces <code>&#34; &#34;</code> as characters. Also; do not return the addendum for those characters that also appear in the <code>discard_list</code>.

Example:

Input:

<pre tabindex="0" class="chroma"><code>sentence = &#34;Interview Query&#34;

discard_list = [&#39;I&#39;,&#39;e&#39;]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>inject_frequency(sentence, discard_list) -&gt; &#34;In1t1er2v1i1ew1 Q1u1er2y1&#34;
</code></pre>

Write a function to return the same string with each character followed by its occurrence count, excluding spaces and discard_list characters

Append Frequency

Write a query to get the cost of all transactions by user ordered by total cost descending.

Example:

Input:

<code>transactions</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>product_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>quantity</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<code>products</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>price</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>
<code>users</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>total_cost</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>
Note: Round the total cost to 2 decimal places.

Write a query to get the cost of all transactions by user ordered by total cost descending

Total Transactions

Given the head of a singly linked list represented as a <code>ListNode</code>, and two zero-indexed positions <code>x</code> and <code>y</code>, write a function <code>swap_node</code> which swaps the positions of nodes <code>x</code> and <code>y</code> and returns the new head. Note that you cannot simply swap the values of these nodes, as these nodes do not have values. Instead, you must swap these two using pointer manipulation (i.e., modifying the <code>next</code> references of the involved nodes inside the list).

A <code>ListNode</code> is defined as:

<pre tabindex="0" class="chroma"><code>class ListNode:
 next: ListNode = None
</code></pre>

Example:

Input:

<pre tabindex="0" class="chroma"><code>linked_list = ListNode(0x01) -&gt; ListNode(0x02) -&gt; ListNode(0x03) 
# Here, imagine that &#39;0x0_&#39; refer to their memory locations.
head = 0x01
x = 1
y = 2
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def swap_node(head, x, y) -&gt; ListNode(0x01) -&gt; ListNode(0x03) -&gt; ListNode(0x02)
</code></pre>

Swapping Nodes

Given an array and a target integer, write a function <code>sum_pair_indices</code> that returns the indices of two integers in the array that add up to the target integer. If not found, just return an empty list.

Note: Can you do it on $O(n)$ time?

Note: Even though there could be many solutions, only one needs to be returned.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>array = [1 2 3 4] 
target = 5 
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def sum_pair_indices(array, target) -&gt; [0 3] or [1 2]
</code></pre>

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>array = [3]
target = 6 
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>Do NOT return [0 0] as you can&#39;t use an index twice.
</code></pre>

Given an array and a target integer, write a function that returns the indices of two integers in the array that add up to the target integer.

Target Indices

Write a Python function called <code>group_anagrams</code> that takes a list of strings as input and returns a list of lists, where each inner list contains a group of anagrams that were present in the input list.

An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, using all the original letters exactly once.

Note: Each of the inner lists should be ordered alphabetically and contain no duplicate values

<h3>Example:</h3>

Input:

<pre tabindex="0" class="chroma"><code>words = [&#34;eat&#34;, &#34;tea&#34;, &#34;tan&#34;, &#34;ate&#34;, &#34;nat&#34;, &#34;bat&#34;]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>[ 
 [&#34;nat&#34;,&#34;tan&#34;],
 [&#34;ate&#34;,&#34;eat&#34;, &#34;tea&#34;],
 [&#34;bat&#34;]
]
</code></pre>

Explanation:

In the example, the words “eat”, “tea”, and “ate” are anagrams of each other, as are the words “tan” and “nat”. The word “bat” does not have any anagrams in the input list, and therefore is listed on its own. The function then groups the anagrams together and returns a list of lists representing these groups.

Each of the lists representing a group of anagrams is sorted in alphabetical order.

Identify the groups of anagrams in a list of words

Groups of Anagrams

How does random forest generate the forest? Additionally, why would we use it over other algorithms such as logistic regression?

What happens when you average the output on multiple decision trees?

What happens when you average the output on multiple decision trees?

Average Trees

How does random forest generate the forest and why use it over logistic regression

Random Forest Explanation

You’re given two tables, payments and users. The payments table holds all payments between users with the <code>payment_state</code> column consisting of either <code>&#34;success&#34;</code> or <code>&#34;failed&#34;</code>. 

How many customers that signed up in January 2020 had a combined (successful) sending and receiving volume greater than $100 in their first 30 days?

Note: The <code>sender_id</code> and <code>recipient_id</code> both represent the <code>user_id</code>.

<code>payments</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>payment_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>sender_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>recipient_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>payment_state</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>amount_cents</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<code>users</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>num_customers</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>

How would you build the recommendation algorithm for type-ahead search for Netflix?

Challenge

<h3>Job Description</h3><div>Job Description<div>Company Description At Brightspeed, we are reimagining how people live, work, play and connect by providing fast, reliable internet connections and an awesome customer experience in twenty states throughout the Midwest and South.Backed by funds managed by Apollo Global Management, our vision is to accelerate the upgrade of copper to fiber optic technologies, bringing faster and more reliable internet service to many rural markets traditionally underserved by broadband providers, while delivering best-in-class customer experience.  Be a part of the team that will make this vision a reality….designing and building a world class fiber network and creating a customer experience second to none.Check us out on the web!  Job Description The Data Analyst is responsible for building and delivering scalable datasets, reports, and analytical solutions that enable data-driven decision-making across Brightspeed. This role partners closely with business stakeholders to understand business needs, translate them into actionable analytics, and deliver accurate, high-quality insights that support strategic and operational objectives. Key Responsibilities <ul><li>Partner with business stakeholders to understand business objectives, define data requirements, and translate business questions into scalable analytical solutions. </li><li>Extract, integrate, validate, and analyze data from multiple internal and external sources to create trusted datasets for reporting and decision-making. </li><li>Develop, maintain, and optimize SQL queries, data pipelines, and analytical models using BigQuery, Python, and other data technologies. </li><li>Design, build, and maintain recurring and ad hoc reports, dashboards, and analytical outputs that provide meaningful business insights. </li></ul><ul><li>Validate data accuracy and integrity by reconciling results across systems, identifying discrepancies, and partnering with stakeholders to resolve data quality issues. </li></ul><ul><li>Analyze trends, patterns, and anomalies, presenting findings through clear visualizations and executive-ready insights that support informed decision-making. </li></ul><ul><li>Support cross-functional initiatives involving data engineering, analytics, reporting, and data warehouse or data mart migrations. </li></ul><ul><li>Contribute to the development and maintenance of scalable datasets, feature stores, and reusable analytical assets that improve reporting efficiency. </li></ul><ul><li>Collaborate effectively across IT, Data, Finance, and business teams to deliver high-quality analytical solutions aligned with organizational priorities. </li></ul><ul><li>Stay current with evolving data technologies and continuously identify opportunities to improve data processes, reporting capabilities, and analytical solutions. </li></ul><ul><li>May perform other duties as assigned. </li></ul>The above statements are intended to describe the general nature and level of work being performed and are not intended to be an exhaustive list of all responsibilities, duties, and skills required. Qualifications Education & Experience <ul><li>Bachelor's degree in Computer Science, Business Analytics, Engineering, Mathematics, Statistics, Information Systems, or a related field. </li></ul><ul><li>Minimum of 5 years of experience developing scalable datasets, reporting solutions, and analytical insights in a business environment. </li></ul><ul><li>Minimum of 3 years of experience working with cloud-based data platforms, preferably Google Cloud Platform (GCP). </li></ul><ul><li>Experience working with large-scale data warehouses, data lakes, or lakehouse environments. </li></ul><ul><li>Professional certifications in Data Analytics, Cloud Technologies, or related disciplines are preferred. </li></ul>Skills & Competencies / Technical Skills <ul><li>Strong proficiency in SQL and Python, with experience using additional scripting or query languages as needed. </li></ul><ul><li>Advanced experience working with Google BigQuery or comparable cloud-based analytical databases. </li></ul><ul><li>Strong understanding of relational database design, data modeling, query optimization, and ETL/ELT concepts. </li></ul><ul><li>Experience integrating data from multiple source systems into consolidated analytical datasets. </li></ul><ul><li>Experience developing reports and dashboards using business intelligence tools. </li></ul><ul><li>Familiarity with cloud data platforms and modern analytics architectures. </li></ul>Business & Analytical Skills <ul><li>Strong analytical thinking with exceptional attention to detail and data accuracy. </li></ul><ul><li>Intellectual curiosity to understand business problems and identify meaningful analytical solutions. </li></ul><ul><li>Ability to navigate ambiguity and solve complex business problems using logical, data-driven approaches. </li></ul><ul><li>Strong communication skills with the ability to translate technical findings into business-friendly insights for executive audiences. </li></ul><ul><li>Excellent collaboration skills and ability to work effectively across technical and non-technical teams. </li></ul><ul><li>Demonstrated ability to prioritize multiple projects and deliver high-quality work in a fast-paced environment. </li></ul>Preferred Qualifications <ul><li>Telecommunications industry experience. </li></ul><ul><li>Experience with data governance, data quality, and metadata management frameworks. </li></ul><ul><li>Experience with business intelligence and visualization platforms such as Tableau, Power BI, or Looker. </li></ul><ul><li>Experience supporting enterprise reporting, financial analytics, or executive dashboards. </li></ul><ul><li>Professional certifications in Google Cloud Platform, Data Analytics, or related technologies. </li></ul>Physical Demands & Work Conditions <ul><li>Primarily office-based or remote office environment with regular use of a computer and standard office equipment. </li></ul><ul><li>Ability to participate in virtual and in-person meetings and collaborate with geographically dispersed teams. </li></ul> #LI-RW1 Additional Information <div></div>WHY JOIN US?We aspire to contemporary ways of working.Recognized as a Top Workplace by the Charlotte Observer, Brightspeed HQ is located on the 7th floor of the new Vantage South End - East Tower in Charlotte, NC. We prioritize hiring talent in the Charlotte area, whenever possible, to make it a truly vibrant destination for our hybrid workforce. At Brightspeed, we have roles that are designated as remote, hybrid, office or field-based, depending on the position, business needs and individual circumstances. We also invest in technology that enables our entire team to stay connected. Why? Because Brightspeed recognizes the value of finding the best talent for the job, wherever they may be.We offer competitive compensation and comprehensive benefits.Our benefits and paid time off programs reflect our underlying belief in promoting overall wellness through physical, emotional and financial health. Brightspeed offers a comprehensive benefit program, including competitive medical, dental, vision, and life insurance; an employee assistance program; a 401K plan with company match and a host of voluntary benefits. Inclusion and belonging are at the center of our grounding belief in Being Real. When we bring our authentic selves to work, everyone is better as a result. A diverse team helps us be fierce advocates for more accessible, inclusive and high-quality internet, because we believe doing so promotes equity in the communities we serve.Brightspeed is an Equal Opportunity Employer that is committed to inclusion of all qualified individuals, including individuals with a disability/veterans. If you require reasonable accommodation to complete a job application or to otherwise participate in the hiring process, please contact taaccommodationrequests@brightspeed.com to initiate the accommodations process. For all applicants, please take a moment to review our Privacy Notices:  <ul><li>Brightspeed’s Privacy Notice for California Residents</li><li>Brightspeed’s Privacy Notice</li></ul></div></div>

<h3>Job Description</h3><div>Job Description<div>Company Description At Brightspeed, we are reimagining how people live, work, play and connect by providing fast, reliable internet connections and an awesome customer experience in twenty states throughout the Midwest and South.Backed by funds managed by Apollo Global Management, our vision is to accelerate the upgrade of copper to fiber optic technologies, bringing faster and more reliable internet service to many rural markets traditionally underserved by broadband providers, while delivering best-in-class customer experience.  Be a part of the team that will make this vision a reality….designing and building a world class fiber network and creating a customer experience second to none.Check us out on the web!  Job Description Role: <ul><li>We are currently looking for a Senior Data Scientist to join our Finance, Strategy & Transformation team at Brightspeed. You will be responsible for developing AI and ML solutions to drive improved business performance and efficiency across domains.  </li></ul>Impact: <ul><li>You will lead end-to-end AI/ML projects from understanding business needs to data preparation, model development, solution deployment, and post-production monitoring. </li></ul><ul><li>You will dissect and solve complex business problems using analytical and quantitative approaches to identify patterns and correlations in large complex data sets. </li></ul><ul><li>You will integrate and curate data from a wide range of internal and external sources to develop rich datasets for predictive & prescriptive modeling as well as machine learning. </li></ul><ul><li>You will define and implement best practices to generate accurate reports, visualizations & dashboards to explain results simply and succinctly to technical and non-technical users. </li></ul><ul><li>You will create models for visual recognition, processing of natural language that analyze complex data to make predictions or decisions, mimicking human intelligence. </li></ul><ul><li>You will identify the most effective model architecture and parameters to drive accuracy and performance. </li></ul><ul><li>You will liaise with stakeholders to understand their needs and concerns and develop concise analytics to provide actionable insights to influence strategy and performance. </li></ul><ul><li>You will build partnerships, share knowledge, and deliver valuable predictive insights to inform strategic decisions, all the while highlighting potential risks and opportunities.     </li></ul>Qualifications You will thrive in this role if you: Required experience• 5+ years of experience of building AI and/or machine learning models for business application• 3+ years of hands-on experience with training, fine tuning, evaluating, and deploying models in production• 3+ years of experience with data lake and cloud services, preferably GCPTrack record of academic rigor and professional certification• Bachelor’s degree or higher in Computer Science, Operations Research, Statistics, Mathematics or related field.• Master’s degree strongly preferred.• Data Science or AI certificationsAnalytical / Technical Skills• Deep expertise in machine learning, neural networks, computer vision, large language models, natural language processing or similar discipline• Demonstrated experience in algorithm selection, model training, feature engineering, fine-tuning performance and implementation• Proficiency in Python and key data science libraries, including Pandas, NumPy, Scikit-learn, Matplotlib and/or Seaborn• Strong capabilities in SQL and experience working with SQL query engines• Experience with Data Visualization tools such as Power BITransformation & Process Improvement• Expertise in Agile methodology for product and software development• Experience with leveraging Data Science and AI to drive business optimizationStructured problem solving & analytical skills• Ability to navigate ambiguous problem contexts and apply critical thinking to identify/diagnose problems and solve with simple, logical solutions• Excellent quantitative skills and data-driven decision-making capabilitiesStrong executive communication• Ability to clearly articulate insights (verbal and written)• Ability to effectively communicate technical and non-technical information and concepts to all levels or organization Unwavering focus on results while creating strong relationships• Ability to work effectively in a fast-paced, dynamic environment, managing multiple priorities and deadlines simultaneously A plus if you have:• Relevant Telecom experience• 2+ years of experience with the design, deployment and evaluation of AI agents and orchestration Physical Demands: • Work is mostly sedentary, performed indoors from a home or company office, while operating a computer and other office productivity machinery, such as a calculator, copy machine and computer printer. #LI-RW1 Additional Information WHY JOIN US?We aspire to contemporary ways of working.We are committed to being a leader in defining a new way to work because we recognize the changing mindset of today's workforce. We are opening a new, state-of-the-art corporate HQ in Charlotte, NC and our current priority is to make it a truly vibrant destination by hiring talent in the greater Charlotte area who are interested in a hybrid remote/office work arrangement. As always, however, we are also open to providing sensible remote options to talent outside of the Charlotte area. Why? Because our purpose is to reimagine how people work, learn, play and connect!We offer competitive compensation and comprehensive benefits.Our benefits and paid time off programs reflect our underlying belief in promoting overall wellness through physical, emotional and financial health. We are committed to building a team as diverse as the customers we serve.Diversity, equity and inclusion are at the center of our grounding belief in Being Real. When we bring our authentic selves to work, everyone is better as a result. A diverse team helps us be fierce advocates for more accessible, inclusive and high-quality internet, because we believe doing so promotes equity in the communities we serve.Brightspeed is an Equal Opportunity Employer<div></div>WHY JOIN US?We aspire to contemporary ways of working.Recognized as a Top Workplace by the Charlotte Observer, Brightspeed HQ is located on the 7th floor of the new Vantage South End - East Tower in Charlotte, NC. We prioritize hiring talent in the Charlotte area, whenever possible, to make it a truly vibrant destination for our hybrid workforce. At Brightspeed, we have roles that are designated as remote, hybrid, office or field-based, depending on the position, business needs and individual circumstances. We also invest in technology that enables our entire team to stay connected. Why? Because Brightspeed recognizes the value of finding the best talent for the job, wherever they may be.We offer competitive compensation and comprehensive benefits.Our benefits and paid time off programs reflect our underlying belief in promoting overall wellness through physical, emotional and financial health. Brightspeed offers a comprehensive benefit program, including competitive medical, dental, vision, and life insurance; an employee assistance program; a 401K plan with company match and a host of voluntary benefits. Inclusion and belonging are at the center of our grounding belief in Being Real. When we bring our authentic selves to work, everyone is better as a result. A diverse team helps us be fierce advocates for more accessible, inclusive and high-quality internet, because we believe doing so promotes equity in the communities we serve.Brightspeed is an Equal Opportunity Employer that is committed to inclusion of all qualified individuals, including individuals with a disability/veterans. If you require reasonable accommodation to complete a job application or to otherwise participate in the hiring process, please contact taaccommodationrequests@brightspeed.com to initiate the accommodations process. For all applicants, please take a moment to review our Privacy Notices:  <ul><li>Brightspeed’s Privacy Notice for California Residents</li><li>Brightspeed’s Privacy Notice</li></ul></div></div>

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

Brightspeed Interview Questions

Brightspeed Interview Guides

Brightspeed Interview Questions

Challenge

Brightspeed Opening Jobs

Discussion & Interview Experiences

Discussion & Interview Experiences