practice a little every day, paws crossed ♡
Interview Questions
Practice 9403 coding, system design and machine learning questions from 546 companies, sorted by role, topic and interview round. Every question has step-by-step hints, a code runner that supports 8 languages and an AI mentor; members also get the full solution walkthrough.
- 9403
- Questions
- 546
- Companies
- 11
- Topics
- 8
- Languages
Showing 151–180 of 781 results
- Boston Consulting GroupEasyData ScientistCalculate Probability of Heads and Red Balls Drawing
This interview question evaluates statistical assumptions, formulas, estimation strategy, uncertainty, edge cases, and interpretation in a realistic interview setting. A strong answer for Calculate Probability of Heads and Red Balls Drawing states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Statistics & MathOnline Assessment - Boston Consulting GroupMediumData ScientistCompute posterior and predictive coin probabilities
This question evaluates Bayesian inference and probabilistic reasoning, focusing on posterior updating, posterior predictive probability, and the conditional expectation of a stopping time given observed outcomes.
Statistics & MathOnline Assessment - Boston Consulting GroupHardData ScientistDetect Data Leakage in Supervised Learning Pipelines
This interview question evaluates core ML concepts, assumptions, math intuition, training/evaluation trade-offs, and practical failure modes in a realistic interview setting. A strong answer for Detect Data Leakage in Supervised Learning Pipelines states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Machine LearningOnline Assessment - Boston Consulting GroupMediumData ScientistImprove Model Generalization with Cross-Validation and Feature Engineering
This interview question evaluates core ML concepts, assumptions, math intuition, training/evaluation trade-offs, and practical failure modes in a realistic interview setting. A strong answer for Improve Model Generalization with Cross-Validation and Feature Engineering states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Machine LearningOnline Assessment - Boston Consulting GroupMediumData ScientistMerge and Clean Customer Order Data for Analysis
This question evaluates proficiency in data manipulation with pandas and SQL concepts, focusing on dataset merging, missing-value handling, and computing derived aggregate columns such as total_spent.
Data Manipulation (SQL/Python)Online Assessment - Boston Consulting GroupMediumData ScientistMerge and Concatenate Inconsistent Order Files with Pandas
This question evaluates proficiency with pandas-based data manipulation, including schema alignment, column renaming, type casting, and vertical concatenation when merging CSV files.
Data Manipulation (SQL/Python)Online Assessment - Boston Consulting GroupEasyData ScientistScale and Normalize: When to Use Each Method?
This interview question evaluates core ML concepts, assumptions, math intuition, training/evaluation trade-offs, and practical failure modes in a realistic interview setting. A strong answer for Scale and Normalize: When to Use Each Method? states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Machine LearningOnline Assessment - Boston Consulting GroupEasyData ScientistTrain GradientBoostingClassifier with 5-Fold Cross-Validation
This interview question evaluates core ML concepts, assumptions, math intuition, training/evaluation trade-offs, and practical failure modes in a realistic interview setting. A strong answer for Train GradientBoostingClassifier with 5-Fold Cross-Validation states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Machine LearningOnline Assessment - ByteDanceMediumSoftware EngineerCount House Segments After Sequential Demolitions
Track the number of consecutive house segments after each requested demolition on an integer line. Each removal can eliminate an isolated segment, trim an endpoint, or split a run, so the solution must update the count efficiently across many distinct positions.
Coding & AlgorithmsOnline Assessment - ByteDanceMediumSoftware EngineerCount Numbers with an Even Number of Digits
Count how many positive integers in an array have an even number of decimal digits. Respect ordinary representations without leading zeroes, count repeated values independently, and handle boundaries such as 10 and 10000 correctly.
Coding & AlgorithmsOnline Assessment - ByteDanceEasyData ScientistImplement several OA simulation problems
This set of problems evaluates skills in string processing, memory simulation and allocation logic, and online data-structure maintenance for dynamic contiguous segment counting, testing algorithmic design and attention to stateful invariants.
Coding & AlgorithmsOnline Assessment - ByteDanceMediumSoftware EngineerSort Every Concentric Matrix Border Clockwise
Sort the values on every concentric border of a rectangular matrix and write them back clockwise from each border's top-left cell. Traverse corners exactly once, preserve interior layer boundaries, handle single-row or single-column centers, and leave the input unchanged.
Coding & AlgorithmsOnline Assessment - C3 AIMediumData ScientistChoose a Parameter to Reduce Underfitting in Gradient-Boosted Trees
Explain why decreasing minimum observations per leaf can reduce gradient-boosted tree underfitting and how to validate the change.
Machine LearningOnline Assessment - C3 AIMediumData ScientistCompare How Models Respond to Multicollinearity
Compare multicollinearity effects in regression, Lasso, logistic regression, decision trees, and boosted trees without overstating immunity.
Machine LearningOnline Assessment - C3 AIMediumSoftware EngineerEvaluate Factual Accuracy and Consistency in a Domain-Specific RAG Chatbot
Evaluate a rare-disease RAG chatbot using domain consistency and expert review, and distinguish factual accuracy from retrieval metrics and lexical overlap.
Machine LearningOnline Assessment - C3 AIMediumData ScientistExplain Training R-Squared After Adding a Random Feature
Prove that ordinary training R-squared cannot decrease when adding a feature, while adjusted and test-set R-squared can.
Statistics & MathOnline Assessment - C3 AIMediumData ScientistExplain the Margin View of Boosting Classification
Understand boosting classification through sequential learners, signed margins, surrogate losses, and the limits of training-margin claims.
Machine LearningOnline Assessment - C3 AIMediumData ScientistIdentify What Does Not Fix Vanishing Gradients
Explain why raising the learning rate does not fix vanishing gradients and compare skip connections, ReLU, and batch normalization.
Machine LearningOnline Assessment - C3 AIMediumSoftware EngineerMaximum-Sum Star with at Most K Arms
Find the maximum node-value sum of a graph star with at most k arms, allowing a center alone and avoiding harmful negative-value leaves.
Coding & AlgorithmsOnline Assessment - CVS HealthMediumData ScientistBuild a leak-free sklearn churn pipeline
This question evaluates practical competencies in building a reproducible scikit-learn churn prediction pipeline—covering temporal splitting to avoid leakage, preprocessing, calibration, hyperparameter tuning, evaluation with ROC AUC/PR AUC and F1-based thresholds, and permutation feature importance—and is in the Machine Learning domain.
Machine LearningOnline Assessment - CVS HealthMediumData ScientistCompute A/B significance, CI, and power
This question evaluates proficiency in statistical inference for A/B testing—specifically two-proportion z-tests, construction of confidence intervals with unpooled standard errors, sample-size and power calculations, and multiple-comparison correction via Bonferroni.
Statistics & MathOnline Assessment - CVS HealthMediumData ScientistCreate Views, Insert, and Update Correctly
This question evaluates SQL data-manipulation competencies including view creation, aggregate joins, INSERT/UPDATE operations, and reasoning about temporal effects on computed aggregates such as historical customer spend.
Data Manipulation (SQL/Python)Online Assessment - CVS HealthMediumData ScientistCreate and query an e-commerce schema
This question evaluates SQL schema design and data manipulation competencies, including defining PostgreSQL table types and constraints, inserting exact datasets, composing aggregate and join queries with date-based filters, and performing DML updates with verification.
Data Manipulation (SQL/Python)Online Assessment - CVS HealthMediumData ScientistImplement R² and Compare PCA With/Without Scaling
This question evaluates a candidate's proficiency with regression evaluation metrics and linear-algebra-based dimensionality reduction, specifically implementing a numerically robust R² scorer and performing PCA with and without feature standardization using NumPy.
Machine LearningOnline Assessment - Capital OneMediumData ScientistAggregate exam scores with NULL handling
This question evaluates proficiency in SQL data manipulation, specifically joins (including LEFT JOIN behavior), NULL handling with ISNULL/COALESCE, conditional aggregation, distinct counts, and date-based filtering within the Data Manipulation (SQL/Python) domain, focusing on practical application of query-writing skills.
Data Manipulation (SQL/Python)Online Assessment - Capital OneEasyData AnalystAnalyze Mission Outcomes and Allocate Response Units
Analyze incident response records to calculate unit win rates, evaluate the impact of rest periods on success, and rank response units using tie-breakers.
Data Manipulation (SQL/Python)Online AssessmentPythonData ManipulationAnalytics - Capital OneMediumData ScientistAnalyze Subscription, Insurance, App, and Card Cases
This question evaluates product analytics competencies—unit-economics, cohort churn modeling, LTV/CAC and funnel math—requiring clear assumptions, metric definitions, governing formulas, and numeric break-even and conversion calculations.
Analytics & ExperimentationOnline Assessment - Capital OneMediumSoftware EngineerApply commands to transform a matrix
This question evaluates array and matrix manipulation skills, specifically in-place row reversal, row swapping, and 90-degree rotation, and falls under the Coding & Algorithms domain with emphasis on practical implementation.
Coding & AlgorithmsOnline Assessment - Capital OneMediumSoftware EngineerBlock-Building Operations: Check Whether a Free Segment Starts at a Position
Process operations on a number line that either place a block at a position or ask whether a segment of a given length starting at a position is free of blocks, and return the answers as a string of ones and zeros. It tests handling interleaved updates and range checks efficiently over large coordinates.
Coding & AlgorithmsOnline Assessment - Capital OneMediumSoftware EngineerCheck Alternating Highs and Lows Around a Circular Array
Check strict high-low alternation around a circular array, including equal neighbors, wraparound comparisons, and the two-element case.
Coding & AlgorithmsOnline Assessment
Boston Consulting Group
C3 AI
CVS Health
Capital One