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Ebsco Information Services Interview Questions

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Data Structures & Algorithms

Write a function moving_window to find the moving window average

Moving Window

Write an algorithm to return the character with the longest continuous repetition, breaking ties by earliest occurrence

Most Repetition

Median O(1)

"Compute the minimum number of parking spots for busses needed. "

Minimum Parking Spots

Write a function list_fifths that returns the fifth-largest number from each list in numlists in ascending order

5th Largest Number

Behavioral

Describing a data project and its challenges

Hurdles In Data Projects

Making data-driven insights actionable for those without technical expertise

Simple Explanations

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

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

Your Strengths and Weaknesses

Write a query to return whether each user's subscription date range overlaps with any other completed subscription

Subscription Overlap

User Experience Percentage

Query Optimization

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

Slow SQL Query

How would you design database indexing for efficient metadata queries when storing large Blobs?

Blob Indexing

Statistics

What are the assumptions of linear regression?

Assumptions of Linear Regression

What is the difference between type I and type II errors?

Type I and II Errors

What are the assumptions of linear regression?

Which assumption of the residuals of the standard linear regression model can not be overcome by increasing the sample size?

Regression assumptions

How would you interpret coefficients of logistic regression for categorical and boolean variables?

Why is one-hot encoding recommended for categorical variables in logistic regression models?

Why is one-hot encoding recommended for categorical variables in logistic regression models?

Coefficients of Logistic Regression

Interpret coefficients of logistic regression for categorical and boolean variables

Machine Learning

Given a table of product subscriptions with a subscription start date and end date for each user, write a query that returns true or false whether or not each user has a subscription date range that overlaps with any other completed subscription.

Completed subscriptions have <code>end_date</code> recorded.

Example:

Input:

<code>subscriptions</code> table

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

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

<tr>
<td><code>start_date</code></td>
<td>DATETIME</td>
</tr>

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

<table>
<thead>
<tr>
<th><code>user_id</code></th>
<th><code>start_date</code></th>
<th><code>end_date</code></th>
</tr>
</thead>

<tbody>
<tr>
<td>1</td>
<td>2019-01-01</td>
<td>2019-01-31</td>
</tr>

<tr>
<td>2</td>
<td>2019-01-15</td>
<td>2019-01-17</td>
</tr>

<tr>
<td>3</td>
<td>2019-01-29</td>
<td>2019-02-04</td>
</tr>

<tr>
<td>4</td>
<td>2019-02-05</td>
<td>2019-02-10</td>
</tr>
</tbody>
</table>
Output:

<table>
<thead>
<tr>
<th><code>user_id</code></th>
<th><code>overlap</code></th>
</tr>
</thead>

<tbody>
<tr>
<td>1</td>
<td>1</td>
</tr>

<tr>
<td>2</td>
<td>1</td>
</tr>

<tr>
<td>3</td>
<td>1</td>
</tr>

<tr>
<td>4</td>
<td>0</td>
</tr>
</tbody>
</table>

Given a table called <code>user_experiences</code>, write a query to determine the percentage of users that held the title of <code>&#34;Data Analyst&#34;</code> immediately before holding the title <code>&#34;Data Scientist&#34;</code>.

Immediate is defined as the user holding no other titles between the <code>&#34;Data Analyst&#34;</code> and <code>&#34;Data Scientist&#34;</code> roles.

Example:

Input:

<code>user_experiences</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>position_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>start_date</code></td>
<td>DATETIME</td>
</tr>

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

<tr>
<td><code>user_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>percentage</code></td>
<td>FLOAT</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>

Google Maps Improvement

Product Sense & Metrics

Write a Python function called <code>longest_increasing_subsequence</code> that takes a list of integers as input and returns as output the length of the longest increasing subsequence in the list.

Note: An increasing subsequence is a subset of a list where the elements are in strictly increasing order. The subsequence does not have to be contiguous or unique.

<h3>Example:</h3>

Input:

<pre tabindex="0" class="chroma"><code>nums = [10, 9, 2, 5, 3, 3, 7, 101, 18]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>4
</code></pre>

Explanation:

The longest increasing subsequence is <code>[2, 3, 7, 101]</code>, for a total length of 4.

Find the longest increasing subsequence in a list of integers.

Longest Increasing Subsequence

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 string <code>str</code> of any length, write an algorithm <code>max_repeating</code> to return which character has the longest string of continuous repetition.

If two characters are tied for most continuous repetition, return the character whose longest continuous repetition occurs earliest in <code>str</code>.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>str = &#39;aabbaaccbbbaa&#39;
def max_repeating(str) -&gt; b
</code></pre>

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>str = &#39;adccccbbbbc&#39;
def max_repeating(str) -&gt; c
</code></pre>

You’re given a list of sorted integers in which more than 50% of the list is comprised of the same repeating integer.

Write a function to return the median value of the list in \(O(1)\) computational time and space.

Note: the lists are all non-empty

Example:

Input:

<pre tabindex="0" class="chroma"><code>li = [1,2,2]
</code></pre>

Output:

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

You’re given <code>numlists</code>, a list where each element is a list of at least five numbers.

Write a function <code>list_fifths</code> that returns a list of the fifth-largest number from each element in <code>numlists</code>. Return the list in ascending order.

Example:

Input:

<pre tabindex="0" class="chroma"><code>numlists = [ [1,2,3,4,5], [3,1,2,5,4], [1,2,3,4,5,6,7], 
[99, 320, 400, 100.25, 55.2, 0.1] ]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def list_fifths(numlists) -&gt; [1, 1, 3, 55.2]
</code></pre>

In the context of hypothesis testing, what are type I errors (type one errors) and type II errors (type two errors)? What is the difference between the two?

Bonus: Describe the probability of making each type of error mathematically.

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

You are given a target value to search. If the value is in the array, then return its index; otherwise, return -1. 

Notes:

<ul>
<li>Rotating an array at pivot \(n\) gives you a new array that begins with the elements after position \(n\) and ends with the elements up to position \(n\).</li>
<li>You may assume no duplicate exists in the array.</li>
</ul>

Bonus: Your algorithm’s runtime complexity should be in the order of \(O(\log n)\).

Example:

Input: 

<pre tabindex="0" class="chroma"><code>sample_input = [0,1,2,4,5,6,7] 
rotated_input = [4,5,6,7,0,1,2]
target_value = 6
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def target_value_search(rotated_input, target_value) -&gt; 2
</code></pre>

Search for a value in log(n) over a sorted array that has been shifted.

Target Value Search

Let’s say you’re in a supermarket.

You’ve found out that there is a huge discount on some items you want; unfortunately, you only have one bag with a certain <code>bag_capacity</code>. Each of the items has its own <code>value</code> and <code>capacity</code>, stored in lists called <code>values</code> and <code>capacities</code> contained in a dictionary called <code>items</code>.

Write a function to pick the items that maximize the total value without exceeding the bag’s capacity and return the total value.

Note: You can’t take more than one copy of each item home. Also, you do not need to fill the entire bag to capacity.

Example:

Input:

<pre tabindex="0" class="chroma"><code>items = {
 &#34;values&#34;:[2,3,1,4],
 &#34;capacities&#34;:[2, 4, 6, 5]
}

bag_capacity = 8
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>max_profit(items,bag_capacity) -&gt; 6
</code></pre>

We choose the first and last item with a total profit of 6 and a capacity of 7, which is less than the <code>bag_capacity</code>.

Write a function to pick the items that maximize the total value without exceeding the bag’s capacity

Filling Supermarket Bag

<h1>Binary Tree Validation</h1>

You are given the root of a binary tree. You need to determine if it is a valid binary search tree (BST).

A valid BST is defined as follows:

<ul>
<li>The left subtree of a node contains only nodes with values less than or equal to the node’s value.</li>
<li>The right subtree of a node contains only nodes with values greater than or equal to the node’s value.</li>
<li>Both the left and right subtrees must also be binary search trees.</li>
</ul>

Given the function <code>def is_valid_bst(root: Node) -&gt; bool:</code>, return True if the binary tree is a valid BST. Otherwise, return False.

<h3>Example:</h3>

Input:

<img src="/s3/questions/9664817c-3e12-4a40-9236-8382b13f55a0.png" alt="image"/>Converted Binary Tree.png

Output:

<pre tabindex="0" class="chroma"><code>def is_valid_bst(Node(3)) -&gt; True
</code></pre>

Given the root node, verify if a binary search tree is valid or not.

Binary Tree Validation

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?

Given a list of numbers <code>nums</code> and an integer <code>window_size</code>, write a function <code>moving_window</code> to find the moving window average.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>nums = [1,2,3,4,5,6]
window_size = 3
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def moving_window(input, window_size) -&gt; [1, 1.5, 2, 3, 4, 5]
</code></pre>

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>nums = [1,2,3,4,5,6]
window_size = 4
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def moving_window(input, window_size) -&gt; [1, 1.5, 2, 2.5, 3.5, 4.5]
</code></pre>

One of the basic steps in parsing string inputs is to check whether the opening and closing characters or tags match, i.e., to check if each opened parenthesis is closed eventually.

Given a list of strings, write a <code>string</code> <code>parser</code> that verifies the integrity of the parenthesis used in the string. The parser should return a list of booleans stating whether that string’s integrity was verified.

Example:

Input:

<pre tabindex="0" class="chroma"><code>list_of_strings = [
 &#39;f(x) + g(x)&#39;, 
 &#39;sin(exp(x)}&#39;, 
 &#39;((())just some string)&#39;, 
 &#39;(4,{(3,4):x**2)&#39;]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def string_parser(list_of_strings) -&gt; [True, False, True, True]
</code></pre>

Given a list of strings, verify whether the parentheses in each string are properly opened and closed.

Check Matching Parentheses

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

Find if there is a path from a starting point to an ending point in a walled maze

Pathfinder in Maze

You are given a graph, which is implemented as a 2D array. Each cell in the array represents a node and the value in the cell represents the cost to traverse to that node. You are also given a start node and an end node. Your task is to implement a function that finds the shortest path from the start node to the end node using any shortest path algorithm.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>graph = [[0, 4, 0, 0, 0, 0, 0, 8, 0],
 [4, 0, 8, 0, 0, 0, 0, 11, 0],
 [0, 8, 0, 7, 0, 4, 0, 0, 2],
 [0, 0, 7, 0, 9, 14, 0, 0, 0],
 [0, 0, 0, 9, 0, 10, 0, 0, 0],
 [0, 0, 4, 14, 10, 0, 2, 0, 0],
 [0, 0, 0, 0, 0, 2, 0, 1, 6],
 [8, 11, 0, 0, 0, 0, 1, 0, 7],
 [0, 0, 2, 0, 0, 0, 6, 7, 0]]
start = 0
end = 4
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>shortest_path(graph, start, end) -&gt; [0, 1, 2, 5, 6, 7, 8, 4]
</code></pre>

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>graph = [[0, 5, 0, 9, 1],
 [5, 0, 3, 0, 2],
 [0, 3, 0, 0, 0],
 [9, 0, 0, 0, 0],
 [1, 2, 0, 0, 0]]
start = 0
end = 2
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>shortest_path(graph, start, end) -&gt; [0, 4, 1, 2]
</code></pre>

The task is to implement a shortest path algorithm (like Dijkstra's or Bellman-Ford) to find the shortest path from a start node to an end node in a given graph. The graph is represented as a 2D array where each cell represents a node and the value in the cell represents the cost to traverse to that node.

Shortest Path Algorithms

Let’s say we’re managing a database for a video-sharing platform where each video is stored as a Blob, and our dataset now exceeds 10 million videos.

How would you configure the database and set up indexing so that queries for video metadata (like title, upload date, or uploader) remain efficient, while also handling the storage and retrieval of large Blob data?

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>

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

Summing Numeric Strings

You are the office manager responsible for scheduling all meetings in a company. Each meeting has a start time and end time, represented as <code>[[start_1, end_1], [start_2, end_2], …]</code>.

Your goal is to find the minimum number of days needed to schedule all meetings without conflicts.

Note: If a meeting ends at the same time another starts, it does not count as a conflict: (2026-12-01 08:00, 2026-12-01 10:00),(2026-12-01 10:00, 2026-12-01 12:00) is not considered a conflict at 10:00.

<h3>Example 1</h3>

Input:

<pre tabindex="0" class="chroma"><code>meetings = [[&#34;2026-12-01 09:00&#34;, &#34;2026-12-01 17:00&#34;], 
 [&#34;2026-12-01 10:00&#34;, &#34;2026-12-01 11:00&#34;], 
 [&#34;2026-12-01 13:00&#34;, &#34;2026-12-01 14:00&#34;]]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def min_days(meetings) -&gt; 2
</code></pre>

Explanation:

<pre tabindex="0" class="chroma"><code>Day 1: [&#34;2026-12-01 09:00&#34;, &#34;2026-12-01 17:00&#34;]
Day 2: [&#34;2026-12-01 10:00&#34;, &#34;2026-12-01 11:00&#34;], [&#34;2026-12-01 13:00&#34;, &#34;2026-12-01 14:00&#34;]
</code></pre>

Since one of the meetings takes the entire working day (from 9 AM to 5 PM), the other needs to be rescheduled to another day; therefore, the answer is 2.

Find the minimum number of days required to schedule all meetings without any conflicts.

Minimum Days for Scheduling All Meetings

How would you convey insights and the methods you use to a non-technical audience?

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 we’ve proposed a new analytics dashboard to a client, but after reviewing our design and data sources, the client says the solution doesn’t meet their needs and pushes back on several key features.

How would you approach the conversation to negotiate alternative solutions, and what steps would you take to ensure disagreements are handled constructively so we can still reach a successful outcome?

Given a list of tuples, each containing two integers representing the arrival and departure time of busses, write a function <code>minimum_parking_spots</code> that computes the minimum number of parking spots needed to accommodate all the busses.

The arrival and departure times are given in hours, ranging from 0 (12:00 AM) to 24 (11:59 PM). Each tuple follows the format <code>(arrival_time, departure_time)</code>.

You may assume that:

<ol>
<li>The arrival and departure times are integers.</li>
<li>A bus only leaves on the next hour after its arrival.</li>
</ol>

Note: A bus can only use a parking spot strictly after it is emptied. This means that a bus leaving at 4 and a bus arriving at 4 require at least two parking spaces.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>busses = [(1, 2), (3, 4), (5, 6)]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def minimum_parking_spots(busses) -&gt; 1
</code></pre>

Explanation:
The first bus arrives at 1 and departs at 2, the second bus arrives at 3 and departs at 4, and the third bus arrives at 5 and departs at 6. At most, there is only one bus at the station at any given time.

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>busses = [(1, 5), (2, 3), (4, 5)]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>def minimum_parking_spots(busses) -&gt; 2
</code></pre>

Explanation:
The first bus arrives at 1 and departs at 5, the second bus arrives at 2 and departs at 3, and the third bus arrives at 4 and departs at 5. At the fourth hour, there are two buses at the station.

Create a class named <code>LRUCache</code> that implements the behavior expected of a Least Recently Used (LRU) Cache.

The <code>LRUCache</code> class implements the following methods:

<ul>
<li><code>__init__(self, capacity)</code> - initializes the object and takes in a capacity parameter specifying the maximum capacity of the cache.</li>
<li><code>get_if_exists(self, key) -&gt; Any|None</code> - gets a value based on a key. If the key exists, returns the associated value. If the key has expired or did not exist in the first place, returns <code>None</code>.</li>
<li><code>put(self, key, value)</code> - places a value inside the cache. In the case wherein the cache is full, invalidates the least recently used element. When two keys collide, the older value should be invalidated in place of the new one.</li>
</ul>

Example:

<pre tabindex="0" class="chroma"><code>cache = LRUCache(2)
cache.put(&#34;sample&#34;, 55)
cache.get_if_exists(&#34;sample&#34;) # returns 55
cache.get_if_exists(&#34;key&#34;) # returns None
cache.put(&#34;hello&#34;, 10) 
cache.put(&#34;sample&#34;, 9)
cache.put(&#34;world&#34;, 5)
cache.get_if_exists(&#34;hello&#34;) # returns None
</code></pre>

Notes:

<ul>
<li>It is assured that the value in the <code>put</code> method will never receive a <code>None</code> value. Moreover, it is assured that the capacity will always be &gt; 0.</li>

<li>All operations must be O(1).</li>

<li>Aside from Python’s standard dictionary implementation (<code>{}</code>), you may not use any other built-in data structures.</li>
</ul>

LRU Cache 1

What is the difference between Logistic and Linear Regression?

When would use one instead of the other in practice?

What is the difference between Logistic and Linear Regression?

Linear vs Logistic Regression

You’re tasked with analyzing data from multiple sources, such as payment transactions, user behavior, and fraud detection logs. How would you approach solving a data analytics problem involving these diverse datasets? What steps would you take to clean, combine, and extract meaningful insights that could improve the system’s performance?

You’re tasked with analyzing data from multiple sources, such as payment transactions, user behavior, and fraud detection logs. How would you approach solving a data analytics problem involving these diverse datasets? What steps would you take to clean, combine, and extract meaningful insights that could improve the system's performance?

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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