Data Scientist Coding & Algorithms Interview Questions
Practice the exact questions companies are asking right now.
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Maximize profit from one stock trade
Problem You are given an integer array prices where prices[i] is the price of a stock on day i. You may complete at most one transaction: choose a day...
Determine earliest collision among moving cars
You are given n cars moving over time. Each car has known initial state at time \(t=0\): - 1D case (straight road): - initial position \(x_i\) (mete...
Find missing numbers in sequences
You are given several number sequences (integers and/or rational numbers). Each sequence contains exactly one missing term written as ?. For each sequ...
Explain list vs tuple in Python
Question In Python: 1. What are the key differences between a list and a tuple? 2. When would you prefer using a tuple over a list? 3. What are the pe...
Find maximum follow depth using recursion
You are given a directed follows relationship representing a social graph: - Each record (follower_id, followee_id) means follower_id follows followee...
Return the largest file size in a directory
Problem (Bash / File System) Implement a Bash function (or shell snippet) that returns the maximum file size (in bytes) under a given directory. Requi...
Return sorted values after quadratic transform
Problem You are given a sorted integer array nums (non-decreasing order) and integers a, b, c that define a quadratic function: \[ f(x) = ax^2 + bx +...
Answer ancestor-walk queries on a rooted tree
Problem (Tree / Parent Array Queries) You are given a rooted tree with n nodes labeled 1..n, represented by a parent array par[1..n]: - par[i] is the ...
Compute bus-on-time and dice-sum probabilities
You are asked two basic probability questions. A) Catching a bus to arrive before a movie A person is going to the cinema. The movie starts in L minut...
Implement factorial and count trailing zeros
Answer the following coding questions in Python. 1) Implement factorial Implement a function factorial(n) that returns \(n!\) for a non-negative integ...
Find minimum swaps to sort array with duplicates
Problem Given an integer array nums of length n that may contain duplicate values, you may perform swaps where you choose any two indices i and j and ...
Match readings with latest same-city humidity
Problem You are given two time-sorted lists of sensor readings: - Temperature records: (time, city, reading) - Humidity records: (time, city, reading)...
Maximize watched duration under consecutive-sum limit
You have a list of videos in a feed. Video i has duration d[i] (positive integer). A user has an “attention span” limit A. You want to select a subset...
Implement four DS coding tasks
You are completing a CodeSignal-style assessment (Python or R). Implement solutions for the following four independent questions. 1) Two-sample z-test...
Add two integer strings using digit-adder
Coding Prompt You are given a helper function: - addDigits(a, b) -> (sumDigit, carry) - a and b are single decimal digits (characters '0'…'9' or int...
Implement palindrome check and valid parentheses
You have 20–25 minutes per problem. Implement the following two functions and be prepared to explain your approach and time/space complexity. Problem ...
Implement nested template string substitution
You are given a dictionary (map) from keys to string templates. Templates may reference other keys using placeholders of the form %KEY%. Example dicti...
Optimize switching puzzle solution
Consider a switching puzzle on an m×n grid of lights where toggling a cell flips its state and that of its orthogonal neighbors (Lights Out variant). ...
Compute maximum concurrent trips from intervals
You’re given n trip intervals [start, end) in seconds, where start < end, representing when a rider’s trip starts and ends in a city on a specific day...
Implement longest increasing subarray with one deletion
Given an array of integers nums, return the length of the longest strictly increasing contiguous subarray you can obtain by deleting at most one eleme...