Data Scientist Coding & Algorithms Interview Questions
Practice the exact questions companies are asking right now.
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Solve two string DP/hash problems
Solve the following two coding questions. 1) Unique Morse Code Transformations You are given an array of strings words (lowercase English letters). Us...
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...
Evaluate piecewise linear function at x
You are given a polyline defined by n 2D points \((x_i, y_i)\). Connecting consecutive points with straight line segments forms a piecewise linear fun...
Merge Two Sorted Lists
You are given the heads of two singly linked lists, each already sorted in non-decreasing order. Merge them into one sorted linked list and return the...
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...
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...
Implement weighted random choice
Implement a simplified version of np.random.choice without calling the built-in function. You are given an array items of length n and an optional pro...
Implement stacks, streaming median, and upward path sum
Complete the following coding problems. State the time/space complexity and key edge cases for each. 1) MinStack Design a stack that supports: - push(...
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...
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 index with positive suffix sums
Given an unsorted integer array \(A\), find an index \(i\) such that every cumulative sum starting from \(i\) to the end of the array is strictly posi...
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...
How do you sample uniformly from an infinite stream?
Coding (Python) — Random sampling from an infinite stream You receive an unbounded/infinite stream of items (e.g., numbers or events). You cannot stor...
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 ...
Traverse an Org Chart by Level
You are given an organization's reporting structure as a flat list of employee-manager relationships. Exactly one employee is the root (the CEO) and h...
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 +...
Implement merge sort and largest 1-rectangle
The coding round included two algorithm questions: 1. Implement merge sort for an array of integers. Return the sorted array and explain its time and ...
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...
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...
Merge two sorted lists
Given two sorted lists (arrays) of integers A and B in non-decreasing order, merge them into a single sorted list. Requirements - Output must be sorte...