The author recounts a full Google China interview experience—including resume submission, recruiter prescreen, phone and onsite coding rounds, HR and English interviews, lunch with engineers, and final feedback—while sharing practical advice and insights to help future candidates prepare effectively.
This article explains what rate limiting is, why it is needed, the typical actions taken when limits are reached, compares single‑node and distributed architectures, reviews four classic limiting algorithms, and provides a practical Redis‑Lua token‑bucket implementation with code examples.
This article presents detailed explanations, algorithmic ideas, and complete Go code for reversing an entire singly linked list, reversing a sub‑list between positions m and n, finding the intersection node of two lists, detecting cycles, and partitioning a list around a pivot value.
This article explains the bitmap concept, demonstrates how to store and query billions of integers using bit-level operations, introduces BitSet for dynamic bit vectors, and describes Bloom filters as probabilistic structures for fast, memory‑efficient membership testing in large‑scale data scenarios.
To boost Xianyu’s user retention, the team built a long‑term promotion platform that combines configurable operational activities with algorithmic SPU recommendations, using Kunpeng extension points, supply‑demand analysis, and conditional search to personalize seller prompts, improve click‑through, and lay groundwork for broader scenario expansion.
This article explains the fundamentals of consistent hashing, compares the classic ring‑based method with the more efficient jump consistent hash algorithm, provides reference implementations in C++, discusses their time‑complexity and practical trade‑offs, and shows how they are applied in systems such as Greenplum.
Given a four‑wheel combination lock with digits 0‑9, the task is to find the minimum number of rotations needed to reach a target combination while avoiding a list of dead‑end states, using a breadth‑first search algorithm illustrated with Java code examples.
This article explains recursive functions, their call mechanics, and demonstrates Python examples for calculating factorials and Fibonacci numbers, highlighting advantages, stack‑overflow risks, and the lack of tail‑recursion optimization in the standard interpreter.
Optical fingerprint sensors capture ridge patterns via illuminated light through an under‑display lens, offering full‑screen designs but facing challenges like incomplete presses, lighting failures, and dirty or wet fingers, while Gabor filter preprocessing enhances image texture to improve recognition robustness and guide future hardware‑algorithm improvements.
This article explains the principles and implementation of Simhash, covering the shortcomings of traditional hash functions, the use of cosine similarity, random projection for dimensionality reduction, locality‑sensitive hashing, and practical optimizations for large‑scale duplicate detection.
The article presents a comprehensive six‑map framework for digital transformation—strategic, business, demand, application, algorithm, and data maps—explaining how enterprises can systematically align goals, processes, requirements, technologies, models, and data assets to achieve effective, data‑driven change.
This article uses the occasion of Tree‑Planting Day to explain binary trees in simple terms, covering their definition, node types, degree, levels, five tree shapes, traversal methods (pre‑order, in‑order, post‑order, level‑order), advantages, drawbacks, and a brief comparison with binary search.
This article explains how to identify "lucky numbers"—elements whose value equals their frequency—in a list by progressively applying Python fundamentals such as set for deduplication, count, map, zip, filter, lambda and sorted, culminating in a concise one‑liner solution.
This article explains the Manhattan routing algorithm used for automatic orthogonal connection routing in diagram tools, discusses its origins, references useful libraries like draw2d, and provides a full TypeScript implementation with code examples and practical application scenarios.
This article presents a comprehensive technical guide on applying Levenshtein and Damerau‑Levenshtein automata to efficiently solve the problem of fast similar‑string lookup in search‑engine systems, introducing novel DFA construction algorithms, theoretical correctness proofs, and practical implementation details with Java code examples.
The paper presents an AB‑testing platform that structures experiments into scenes, buckets, layers and traffic, uses a salted‑hash based allocation and a two‑step “multi‑withdraw‑fill” algorithm to adjust percentages while preserving user‑experiment stability, and describes a lightweight, cache‑centric system architecture with staggered config reloads and safeguards against database spikes and zombie nodes.
This article introduces the business background and security challenges of 58.com, explains the three‑layer intelligent risk‑control architecture built on big‑data and AI, and details practical methods for perceiving and detecting unknown risks using techniques such as PU learning, Prophet, and HotSpot.
This article reviews the 2020 achievements of Alibaba.com’s ICBU algorithm team, explaining the evolving role of algorithm engineers, the fundamentals of e‑commerce algorithms, the team’s three‑pillar workflow of Understanding, Growth, and Matching, and the technical breakthroughs that drove business impact and future directions.
This article explains a method for detecting video stutter by converting uploaded videos into frame sequences with ffmpeg, calculating pixel differences between consecutive frames, aggregating motion metrics, removing scene‑change effects, computing a dynamic factor, and outputting a binary result indicating the presence or absence of stutter.
This article explains how to limit the number of requests an IP can make to a specific API endpoint within a sliding time window using Redis list structures in PHP, including example scenario, implementation logic, and complete code snippets.
This article explains the fundamentals of rate limiting, its importance for high‑availability services, various classification dimensions, common algorithms such as fixed‑window, sliding‑window, leaky‑bucket and token‑bucket, and demonstrates practical usage with Go's golang.org/x/time/rate library including code examples and configuration tips.
This article explains several Java techniques—including a simple loop, String.split, and regular‑expression approaches—to compute the maximum number of consecutive '1' characters in a binary string, and even extends the method to handle mixed‑character inputs.
This article explains the core concepts of recursion by walking through an array‑sum example and a LeetCode linked‑list removal problem, detailing the necessary base case, recursive formula, and providing complete Java implementations with step‑by‑step visual illustrations.
This article explains Twitter's Snowflake algorithm, detailing its 64‑bit structure, the role of each bit segment, a step‑by‑step Java implementation, and the algorithm's performance advantages and practical limitations in distributed backend systems.
This article explains load‑balancing fundamentals, covering hardware vs. software devices, server‑side and client‑side balancing, and walks through common algorithms—random, weighted random, round‑robin, weighted and smooth weighted round‑robin, hash, consistent hash with virtual nodes, and least‑connection—each illustrated with Java code examples and diagrams.
This tutorial presents thirty concise Python tasks—ranging from duplicate detection and anagram checking to list chunking, dictionary merging, and execution timing—each accompanied by clear explanations and ready‑to‑run code snippets, enabling beginners to solidify fundamental concepts through hands‑on practice.
This article explains how to solve LeetCode's "Add Two Numbers" problem by representing integers with reversed linked lists in Java, detailing both an iterative method and a recursive solution, complete with code examples and analysis of time and space complexities.
This article explains the fundamentals of recommendation systems, covering data collection, user and content profiling, system architecture, algorithmic pipelines such as recall, filtering, ranking, and evaluation metrics, while also discussing practical challenges like echo chambers and long‑term user value.
From the rise and fall of Flash to modern front‑end video playback techniques, performance optimization strategies, AI recommendation fundamentals, CLI design best practices, and a glimpse into game development and algorithm analysis, this article surveys diverse cutting‑edge technologies shaping today’s software landscape.
This article explains the cardinality‑counting problem behind DAU/MAU and unique visitor metrics, compares naïve solutions like Set, Bitmap and Bloom filter, introduces big‑data algorithms such as Linear Counting, LogLog and HyperLogLog, and shows how Redis implements HyperLogLog with dense and sparse storage optimizations.
This article explains what Armstrong (narcissistic) numbers are, demonstrates how to determine them for three‑digit, n‑digit, and range‑based cases, and provides clear Python code examples with sample outputs to help readers grasp the concept and implement the checks.
The article analyzes how to update the positions of intermediate points on a wire when the user drags the wire with the mouse, compares three solution approaches—including point‑wise rotation and scaling, a complex geometric construction, and a unified transformation matrix—and summarizes their trade‑offs.
This article provides a comprehensive analysis of the Soul social app, examining its non‑hormonal positioning, community atmosphere, relationship‑chain metrics, content‑driven engagement, algorithmic matching, and future growth strategies, highlighting how these factors drive user retention and scale.
This article revisits Jump Consistent Hash, analyzes the O(n) bottleneck of the original algorithm, derives a probability‑based selection method that achieves O(log n) complexity, and provides a Go implementation demonstrating the optimized approach.
This article explains heap sort by introducing its theory, visual step‑by‑step construction of a max‑heap, a complete Python implementation, and an analysis of its time and space complexities, including detailed code walkthrough and complexity derivations.
The article explains how to use a circular doubly‑linked list together with a Union‑Find (disjoint‑set) structure to merge electrically equivalent points, split a circuit graph into connected sub‑graphs, and provides a full TypeScript implementation with practical considerations.
This article introduces a straightforward Java implementation of a sliding‑window rate‑limiting algorithm for single‑machine use, explains its core logic, demonstrates its behavior with sample output, and visualizes the step‑by‑step process of how timestamps are managed within the window.
This article describes a video stutter detection method that converts video to a frame sequence, computes pixel differences between consecutive frames, aggregates motion energy, applies scene‑cut compensation and a dynamic threshold to output a binary indicator of stutter presence.
This article uses the popular Chinese card game Three Kingdoms to illustrate the Byzantine Generals Problem, explaining its relevance to distributed consensus, outlining four foundational theories and eight protocols, and demonstrating how voting, message tampering, and signature mechanisms affect agreement among nodes.
The article compares an adjacency‑list approach and a circular doubly linked list for representing circuit connections, showing that the linked‑list method achieves O(1) connect/disconnect operations with linear space, making it the most efficient and simple solution for graph‑based circuit modeling.
This article introduces recursion, explains its core principles, presents a general problem‑solving approach, and walks through multiple practical examples—from factorial and climbing stairs to binary tree inversion and the Tower of Hanoi—while analyzing time and space complexities and offering optimization techniques.
This article explains a promotional bottle‑exchange problem, presents example inputs and outputs, and demonstrates two greedy‑algorithm implementations in Java that compute the maximum number of bottles one can drink when empty bottles can be exchanged for new ones.
In this live talk, Dr. Zhang Renyu, an assistant professor at NYU Shanghai and economist at Kuaishou, presents his research on optimizing cold-start problems in feed advertising using a novel Shadow Bidding with Learning (SBL) algorithm, detailing its design, implementation, and experimental results.
On November 7, 2020, Hulu’s Shulei presented how the company’s video advertising platform employs AI-driven algorithms—including binge‑watch prediction, inventory forecasting with Prophet, and a PID‑controller based real‑time allocation system—to enhance targeting, optimize revenue, and improve user experience.
This article explains the O(log N) efficiency of binary search, provides a clear template implementation in code, highlights common pitfalls, and presents two useful variants for finding the first equal or first greater‑or‑equal element in a sorted array.
This article explains how the classic PID feedback control algorithm can be adapted to regulate advertising bidding costs, describing its theory, component effects, practical implementation in a real‑time ad‑exchange, simulation experiments, and the resulting improvements in budget adherence and cost stability.
The article explains how to sort a massive 4.6 GB file containing 500 million random integers by first attempting in‑memory quicksort and merge sort, then using a bitmap approach, and finally applying an external sort that splits the data into manageable chunks and merges them efficiently.
This article explains why data consistency is essential in distributed systems, defines consistency, compares strong and eventual consistency, and details the design and operation of major algorithms such as Paxos, Multi‑Paxos, Raft, ZAB, and Gossip with illustrative examples and diagrams.
This article examines JD.com’s transition from traffic‑driven acquisition to a data‑centric, algorithm‑powered membership model, detailing the construction of a robust data foundation, multi‑level analysis methods, productized dashboards, and growth‑hacking experiments that boosted PLUS member retention and revenue.
This article explains how to remove duplicates from a sorted array in‑place using Python, detailing the problem constraints, providing two illustrative examples, outlining a simple iteration‑based solution approach, and presenting a complete code implementation that operates with O(1) extra space.
This article explains the internal structure and algorithms of Java’s HashMap, covering its array‑based storage, collision handling with linked lists and red‑black trees, key methods like put, get, resize, and thread‑safety considerations, complete with code examples and diagrams.
The article explores the concept of the comfort zone, shares the personal journey of Alibaba DAMO Academy senior algorithm expert Fei Ying, and offers practical advice on career growth, AI research, and leveraging VR/AR technologies to drive innovation.
This article walks you through Hulu's 2021 campus recruitment update, explains the online programming test schedule and format, shares interview tips, and provides detailed statements, sample I/O, and solution analyses for four algorithmic problems covering probability, array maxima, maze navigation, and segment‑tree optimization.
Xianyu’s new attribute completion system combines MetaQ messaging, AI image recognition, and offline option configuration to auto‑populate key product details, incentivize sellers, and iteratively refine attributes via sales metrics, boosting structured coverage by 30%, cutting verification time 70%, and raising UV‑CTR around three percent.
This article introduces the KMP string‑matching algorithm, explains its practical scenarios, details the construction and purpose of the Next array, provides a step‑by‑step Python implementation, and analyzes its linear‑time complexity for efficient pattern searching.
China’s latest revision of its technology export control catalogue adds data‑driven personalized push technology, potentially barring TikTok’s core algorithm from export, and experts advise firms like ByteDance to pause negotiations and complete licensing procedures amid heightened regulatory scrutiny.
This article showcases a collection of intriguing code snippets—including a two‑line shuffle algorithm, the unconventional Sleep Sort technique, a minimalist AI core loop, a simple method to get tomorrow’s timestamp, and the mysterious 0x5f375a86 fast inverse square root trick.
This article explains three common round‑robin scheduling algorithms—simple, weighted, and smooth weighted—detailing their logic, step‑by‑step execution, PHP implementation, and the trade‑offs of each approach in distributed systems.
The presentation explains how a multi‑task guarantee optimization algorithm—illustrated with Youku’s new hot series—builds an exposure‑sensitivity model to allocate limited video‑placement resources across homepage and channel slots, overcoming manual rule limitations and simultaneously maximizing play counts while satisfying diverse scenario and content objectives.
The author shares a detailed, six‑round Google China engineering interview experience—including personal background, each interview stage from recruiter prescreen to onsite sessions, typical coding and algorithm questions, system‑design challenges, and practical tips for preparation and follow‑up.
This article explains the principles of short URL generation, compares incremental ID, hash, and random algorithms, analyzes their security and collision characteristics, and presents a complete backend design including database schema, caching strategy, sharding, and Java implementation details.
This article examines how short‑video platforms can expand into new user circles by leveraging external trend data, competitive analysis, KOL resources, precise content matching, and data‑driven product strategies to acquire, retain, and reactivate users while balancing growth and platform health.
This article explains the purpose of flow control, compares various rate‑limiting algorithms—including simple window, sliding window, leaky bucket, token bucket, and sliding log—provides Java interface definitions and code examples, discusses their complexity, precision, smoothness, and suitability for single‑machine and distributed scenarios, and offers practical deployment tips using Sentinel, Nginx, Guava, Tair, and Redis.
This article explains what load balancing is, why it is essential for scaling web services, outlines the four OSI‑layer classifications, compares popular software balancers such as LVS, Nginx and HAProxy, and reviews common static and dynamic load‑balancing algorithms with their advantages and use cases.
This article explains the Delaunay triangulation concept, its geometric properties such as empty circumcircles and maximal minimum angles, and presents a detailed divide‑and‑conquer algorithm with step‑by‑step merging logic and a complete TypeScript code implementation.
This article explains the classic Dutch National Flag problem, describes the three‑way partition algorithm with pointer analysis, and provides concise Python and Go implementations that sort an array of red, white, and blue elements in linear time and constant space.
This article presents a data‑driven approach for allocating limited video exposure resources by building a PV‑click‑CTR (P2C) sensitivity model and a multi‑objective optimization framework that balances overall view volume and fairness across scenes, validated through offline metrics and online bucket tests.
The article recounts three technical interview problems—a list‑index extraction using a hash map, a tree‑path reconstruction from parent identifiers, and a minimum‑path‑sum dynamic‑programming challenge—providing Python code solutions and brief explanations for each.
This article introduces Didi's adaptive grouping algorithm, which enhances the uniformity of user allocation in AB experiments by replacing traditional complete randomization with a single-pass method that balances observed metrics across groups, and demonstrates its effectiveness through large‑scale experimental results.
Didi’s AI Lab introduces an Adaptive grouping algorithm for its Apollo AB‑testing platform that allocates users in a single pass using direct and indirect scores, achieving over 95 % balance probability and reducing group imbalance from 14 % (CR) and 2.7 % (RR) to under 0.8 %.
This article explains how to determine whether any four playing cards can be combined using addition, subtraction, multiplication, and division (with parentheses) to reach 24, presenting two Python implementations—an exhaustive enumeration method and a more efficient recursive combination technique—along with performance comparisons.
The article demonstrates how to solve a sixth‑grade geometry problem by programmatically drawing the figure with Python, randomly sampling points inside a rectangle, and estimating the shaded region's area through Monte‑Carlo simulation, achieving results close to the exact answer.
This article presents a combinatorial fish‑division puzzle solved by exhaustive search with Python code, followed by clear explanations and Python implementations of three fundamental sorting algorithms—merge sort, selection sort, and bubble sort—illustrating their core ideas and step‑by‑step processes.
This article examines Python execution speed by benchmarking simple arithmetic, logical checks, built‑in functions like max, and three class‑based point‑in‑rectangle implementations, revealing that straightforward if‑statements are often fastest while highlighting practical tips for writing performant Python code.
This article demonstrates a PHP class that implements the WeChat red packet splitting algorithm, explaining the constraints, providing a complete source code example, and showing how to instantiate the class to distribute a total amount into a specified number of packets with a minimum value.
This article explores various distributed ID generation methods, focusing on Twitter's Snowflake algorithm, detailing its structure, advantages, drawbacks, and comparisons with UUID, database auto-increment, and Redis, while providing implementation insights and references to related open-source solutions.
This article explains the two key properties of recursive functions, demonstrates Python's default recursion depth limit and how to adjust it, discusses the drawbacks of recursion, and presents a programming task to implement a recursive Fibonacci‑triangle generator with sample code.
The article explains how limited hash spaces cause collisions, then compares open hashing (separate chaining) and closed hashing techniques—linear probing, double hashing, and random hashing—detailing their insertion, search, and deletion algorithms along with the performance trade‑offs and load‑factor analysis for each method.
This article explains how to implement a priority queue in Python using the built‑in heapq module, demonstrates extracting smallest and largest elements from price lists, and provides a full PriorityQueue class with push, pop, and is_empty methods, illustrated with stock portfolio examples.
This article provides a thorough introduction to heap data structures, covering their definition, core operations such as insertion and deletion, heap sort implementation, and practical production use cases like priority queues, Top‑K queries, and TP99 calculation, all illustrated with Java code examples.
This article explains the Boyer‑Moore string‑matching algorithm, detailing how the bad‑character and good‑suffix heuristics dramatically reduce comparisons, and provides a complete Java implementation with step‑by‑step illustrations of each matching round and the underlying shift calculations.
This article introduces the open‑source “Fucking Algorithm” project, a popular GitHub collection of over 60 LeetCode‑based articles that explain algorithm problems with detailed reasoning, aiming to improve developers' problem‑solving mindset and algorithmic thinking.
This article explains the brute‑force (BF) substring search algorithm, demonstrates its step‑by‑step operation with examples, then introduces a simple hash‑based sliding‑window method (a basic Rabin‑Karp approach), provides Java code, and shows how to compute and update hashes efficiently to locate a pattern in a main string.
This article explores how large wealth‑management platforms can model product recommendation as a mapping between customers and financial products, defines various evaluation goals such as transaction volume, revenue and user satisfaction, and outlines a systematic A/B‑testing workflow for comparing and optimizing recommendation algorithms.
This article explains how Youku combined user‑growth objectives with real‑time bidding (RTB) advertising, designing and optimizing DSP algorithms to maximize high‑value daily active users under cost constraints, covering business background, RTB mechanics, ranking models, pricing strategies, engineering pipelines, and future directions.
This article introduces the basics of bitwise operations, common operators, practical tricks such as checking parity, setting or clearing bits, and demonstrates their use in solving classic algorithmic challenges like the poison bottle puzzle, power‑of‑two detection, counting set bits, and the 8‑Queens problem.
This article explains the concept of user profiling, outlines an eight‑dimensional tag architecture, describes step‑by‑step methods for constructing a robust profile system from scratch and expanding it, and shows how these profiles support statistical analysis, targeted marketing, and recommendation algorithms.
This article explains the Brute‑Force (BF), Boyer‑Moore (BM), and Knuth‑Morris‑Pratt (KMP) string‑matching algorithms, illustrates their operation with step‑by‑step visual examples, discusses the inefficiencies of BF, the shift rules of BM, and the prefix‑suffix logic of KMP, and provides a complete Java implementation including the construction of the next array.
This article explains how to transform a number like 1234 into a reversed list of its digits using both a straightforward string method and two recursive implementations—standard and tail recursion—while noting Python's general preference for iterative solutions.
Kunpeng, a three‑level advertising framework for Xianyu, unifies activity‑scene‑material abstraction, extensible DataFetcher and modular filter libraries, and a global traffic‑mixing algorithm, enabling business groups to self‑service material delivery, achieve 60‑100% conversion gains, cut UV cost by ~40% and halve time‑to‑market.
This article walks through a common Java interview problem of checking if an integer is odd, presenting multiple candidate solutions, explaining their shortcomings, and culminating in an optimal bitwise implementation while also discussing performance misconceptions.
This article explains the sliding‑window technique for solving the classic “Longest Substring Without Repeating Characters” problem, presents step‑by‑step analysis, demonstrates three Java implementations—from a basic set‑based method to hashmap and array optimizations—and discusses their time‑complexity improvements.
This article explains the binary search algorithm for locating a target element in a sorted array, describing its midpoint‑starting process, halving of the search range, termination conditions, and includes a simple example with its output.
This tutorial explains how to use Python's turtle graphics and the random module to draw a 3×3 magic square, covering functions for drawing squares, filling colors, displaying numbers, and a brute‑force algorithm that shuffles numbers until the magic‑square condition is met.
The article presents an AI‑driven follow‑subtitle system for video streaming that uses server‑side face detection and tracking to attach speech‑bubble bullets to characters, synchronizing trajectories with playback via a client SDK, while addressing cut‑scene handling, latency, and power constraints.
This article explains the principle of jump consistent hashing, compares it with traditional ring‑based methods, shows a step‑by‑step implementation with Go code, and discusses its performance advantages and potential optimizations for distributed key‑value storage systems.
This article introduces the concept of trees and binary search trees, defines a C struct for tree nodes, and provides complete implementations for creating nodes, inserting, deleting, searching, finding min/max, computing size and height, as well as recursive and non‑recursive traversals including pre‑order, in‑order, post‑order and level‑order.
This article explores how to sort a massive 4.6 GB file containing 500 million random integers by applying internal quicksort with median‑of‑three, merge sort, a bitmap‑based approach, and an external‑merge strategy, comparing their performance, memory usage, and implementation details in Java.
This article demonstrates two Python programming exercises: generating all unique three‑digit numbers from digits 1‑4 using nested loops, and calculating a tiered profit‑based bonus by segmenting profit ranges, complete with source code, analysis, and sample outputs.
This article explains how to enumerate every permutation of an array using a depth‑first search backtracking algorithm, illustrates the process with a tree diagram, compares DFS with BFS, and provides a complete C implementation along with a generic Python template.
