Neural Mastery

Practice AI

Short, focused coding problems — implement the function yourself in a real, in-browser Python sandbox, run it against real test cases (pass/fail, no LLM grading), then reveal a reference solution with the reasoning behind it. Inspired by the format of deep-ml.com — original problems, tied to the concept pages already on this site.

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TitleDifficultyTopicStatusPoints
Dot Product From ScratcheasyMathematics for AINot started50 ptsBatch Dot ProductmediumMathematics for AINot started50 ptsMatrix Multiplication From ScratchmediumMathematics for AINot started50 ptsMean Squared Error From ScratcheasyMachine LearningNot started50 ptsWeighted RMSEmediumMachine LearningNot started50 ptsOne Gradient Descent Step for Linear RegressionmediumMachine LearningNot started50 ptsK-Means, One Assignment StepmediumMachine LearningNot started50 ptsK-Means, Centroid Update StepmediumMachine LearningNot started50 ptsSigmoid Activation From ScratcheasyDeep LearningNot started50 ptsSigmoid Derivative (Vectorized, Numerically Stable)mediumDeep LearningNot started50 ptsNumerically Stable Softmax From ScratchmediumDeep LearningNot started50 ptsSoftmax Gradient (Vector-Jacobian Product)hardDeep LearningNot started50 ptsPair With Target SumeasyInterview PrepNot started50 ptsLongest Run of Unique CharactersmediumInterview PrepNot started50 ptsFind the Rotation PointeasyInterview PrepNot started50 ptsMaximum Non-Adjacent SummediumInterview PrepNot started50 ptsThe Lone NumbereasyInterview PrepNot started50 ptsThe Gap in the SequencemediumInterview PrepNot started50 ptsLargest Rectangle in a SkylinehardInterview PrepNot started50 ptsSample Mean and Variance From ScratcheasyMathematics for AINot started50 ptsStandardize a Dataset (Z-Score Normalization)mediumMathematics for AINot started50 ptsBayes' Theorem, Posterior From ScratchmediumMathematics for AINot started50 ptsNumerical Gradient via Finite DifferencesmediumMathematics for AINot started50 ptsCosine Similarity From ScratcheasyNLPNot started50 ptsPairwise Cosine Similarity MatrixmediumNLPNot started50 ptsTF-IDF Weight From ScratchmediumNLPNot started50 pts2D Convolution From ScratchmediumComputer VisionNot started50 ptsDiscounted Return From ScratcheasyReinforcement LearningNot started50 ptsFull Return-to-Go SequencemediumReinforcement LearningNot started50 ptsDesign a Min StackmediumInterview PrepNot started50 ptsMerge K Sorted ListshardInterview PrepNot started50 ptsShortest Path in an Unweighted GraphmediumInterview PrepNot started50 ptsCount Islands (Connected Components)mediumInterview PrepNot started50 ptsDetect a Cycle in a Directed GraphhardInterview PrepNot started50 ptsLevel-Order Traversal (BFS)easyInterview PrepNot started50 ptsValidate a Binary Search TreemediumInterview PrepNot started50 ptsLowest Common Ancestor in a Binary TreehardInterview PrepNot started50 ptsThree Sum to ZeromediumInterview PrepNot started50 ptsMinimum Window SubstringhardInterview PrepNot started50 ptsSearch in a Rotated Sorted ArraymediumInterview PrepNot started50 ptsLongest Increasing SubsequencehardInterview PrepNot started50 ptsThe Two Lone NumbershardInterview PrepNot started50 ptsFind All Duplicates in an ArraymediumInterview PrepNot started50 ptsDaily TemperaturesmediumInterview PrepNot started50 ptsDesign an LRU CachehardInterview PrepNot started50 ptsSmallest Range Covering Elements from K ListshardInterview PrepNot started50 ptsRotting Oranges (Multi-Source BFS)mediumInterview PrepNot started50 ptsRight Side View of a Binary TreemediumInterview PrepNot started50 ptsParallel Sum Reduction (WebGPU)mediumMLOpsNot started50 ptsDesign Challenge: A RAG System Over 100M Enterprise DocumentsDesignML System DesignNot started100 ptsDesign Challenge: Real-Time Fraud Detection at 100K Events/SecDesignML System DesignNot started100 ptsDesign Challenge: A Support Agent That Can Actually Take ActionsDesignML System DesignNot started100 ptsDesign Challenge: Personalized Recommendations for a 50M-Item CatalogDesignML System DesignNot started100 pts