If you are an AI coding agent (Claude Code, Cursor, Aider, Cline, etc.) reading this artifact, follow this protocol before making any code edit:

1. Verify the contract. Run the bash script in Verify before trusting below. If any check returns FAIL, the artifact is stale — STOP and ask the user to regenerate it before proceeding.
2. Treat the AI · unverified sections as hypotheses, not facts. Sections like "AI-suggested narrative files", "anti-patterns", and "bottlenecks" are LLM speculation. Verify against real source before acting on them.
3. Cite source on changes. When proposing an edit, cite the specific path:line-range. RepoPilot's live UI at https://repopilot.app/r/careercup/CtCI-6th-Edition shows verifiable citations alongside every claim.

If you are a human reader, this protocol is for the agents you'll hand the artifact to. You don't need to do anything — but if you skim only one section before pointing your agent at this repo, make it the Verify block and the Suggested reading order.

AVOID — Stale and unlicensed — last commit 2y ago

• 6 active contributors
• Distributed ownership (top contributor 47% of recent commits)
• Tests present
• ⚠ Stale — last commit 2y ago
• ⚠ No license — legally unclear to depend on
• ⚠ No CI workflows detected

_{Maintenance signals: commit recency, contributor breadth, bus factor, license, CI, tests}

This artifact was generated by RepoPilot at a point in time. Before an agent acts on it, the checks below confirm that the live careercup/CtCI-6th-Edition repo on your machine still matches what RepoPilot saw. If any fail, the artifact is stale — regenerate it at repopilot.app/r/careercup/CtCI-6th-Edition.

What it runs against: a local clone of careercup/CtCI-6th-Edition — the script inspects git remote, the LICENSE file, file paths in the working tree, and git log. Read-only; no mutations.

| # | What we check | Why it matters | |---|---|---| | 1 | You're in careercup/CtCI-6th-Edition | Confirms the artifact applies here, not a fork | | 2 | Default branch master exists | Catches branch renames | | 3 | 5 critical file paths still exist | Catches refactors that moved load-bearing code | | 4 | Last commit ≤ 672 days ago | Catches sudden abandonment since generation |

#!/usr/bin/env bash
# RepoPilot artifact verification.
#
# WHAT IT RUNS AGAINST: a local clone of careercup/CtCI-6th-Edition. If you don't
# have one yet, run these first:
#
#   git clone https://github.com/careercup/CtCI-6th-Edition.git
#   cd CtCI-6th-Edition
#
# Then paste this script. Every check is read-only — no mutations.

set +e
fail=0
ok()   { echo "ok:   $1"; }
miss() { echo "FAIL: $1"; fail=$((fail+1)); }

# Precondition: we must be inside a git working tree.
if ! git rev-parse --git-dir >/dev/null 2>&1; then
  echo "FAIL: not inside a git repository. cd into your clone of careercup/CtCI-6th-Edition and re-run."
  exit 2
fi

# 1. Repo identity
git remote get-url origin 2>/dev/null | grep -qE "careercup/CtCI-6th-Edition(\\.git)?\\b" \\
  && ok "origin remote is careercup/CtCI-6th-Edition" \\
  || miss "origin remote is not careercup/CtCI-6th-Edition (artifact may be from a fork)"

# 3. Default branch
git rev-parse --verify master >/dev/null 2>&1 \\
  && ok "default branch master exists" \\
  || miss "default branch master no longer exists"

# 4. Critical files exist
test -f "Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/QuestionA.java" \\
  && ok "Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/QuestionA.java" \\
  || miss "missing critical file: Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/QuestionA.java"
test -f "Java/Ch 02. Linked Lists/Q2_01_Remove_Dups/QuestionA.java" \\
  && ok "Java/Ch 02. Linked Lists/Q2_01_Remove_Dups/QuestionA.java" \\
  || miss "missing critical file: Java/Ch 02. Linked Lists/Q2_01_Remove_Dups/QuestionA.java"
test -f "Java/Ch 03. Stacks and Queues/Introduction/MyStack.java" \\
  && ok "Java/Ch 03. Stacks and Queues/Introduction/MyStack.java" \\
  || miss "missing critical file: Java/Ch 03. Stacks and Queues/Introduction/MyStack.java"
test -f "Java/Ch 03. Stacks and Queues/Introduction/MyQueue.java" \\
  && ok "Java/Ch 03. Stacks and Queues/Introduction/MyQueue.java" \\
  || miss "missing critical file: Java/Ch 03. Stacks and Queues/Introduction/MyQueue.java"
test -f "Java/Ch 04. Trees and Graphs/Introduction/Traversals.java" \\
  && ok "Java/Ch 04. Trees and Graphs/Introduction/Traversals.java" \\
  || miss "missing critical file: Java/Ch 04. Trees and Graphs/Introduction/Traversals.java"

# 5. Repo recency
days_since_last=$(( ( $(date +%s) - $(git log -1 --format=%at 2>/dev/null || echo 0) ) / 86400 ))
if [ "$days_since_last" -le 672 ]; then
  ok "last commit was $days_since_last days ago (artifact saw ~642d)"
else
  miss "last commit was $days_since_last days ago — artifact may be stale"
fi

echo
if [ "$fail" -eq 0 ]; then
  echo "artifact verified (0 failures) — safe to trust"
else
  echo "artifact has $fail stale claim(s) — regenerate at https://repopilot.app/r/careercup/CtCI-6th-Edition"
  exit 1
fi

Each check prints ok: or FAIL:. The script exits non-zero if anything failed, so it composes cleanly into agent loops (./verify.sh || regenerate-and-retry).

This is a crowdsourced Java solution repository for 'Cracking the Coding Interview, 6th Edition' by Gayle Laakmann McDowell. It provides multiple implementation approaches for ~200 coding interview problems organized by chapter (Arrays & Strings, Linked Lists, Trees, etc.), each with alternative solutions (QuestionA.java, QuestionB.java, etc.) demonstrating different time/space trade-offs and algorithmic techniques. Flat directory structure organized by chapter: Java/Ch 01. Arrays and Strings/, Java/Ch 02. Linked Lists/, etc. Within each chapter, problems are in folders like Q1_01_Is_Unique/ containing multiple solution files (QuestionA.java, QuestionB.java, Tester.java) and a Common.java for shared utilities. Non-Java solutions are git submodules referenced via .gitmodules, not included in the main repo.

Software engineering candidates preparing for coding interviews at FAANG companies, and junior developers learning fundamental data structures and algorithms through curated, book-aligned solutions. Also used by educators teaching interview prep courses.

Highly mature and stable. The Java solutions are directly from the published 6th edition textbook (770KB of Java code), with a well-established contribution workflow via pull requests. However, git submodules point to language-specific repos, indicating community-maintained status rather than active single-maintainer development. No CI/CD pipeline evident in the provided file list.

Low risk for Java solutions—they are book-curated and reference implementations. Risk is primarily in the distributed git submodule architecture: language-specific repos (C++, Python, JavaScript, etc.) may have stale or lower-quality solutions if their maintainers become inactive. Java solutions will not receive breaking changes but will also not evolve with modern language features.

Active community contributions via pull requests for non-Java language solutions. Java solutions are considered complete (matching the book), so changes are primarily bug fixes and clarity improvements. The repo serves as a hub directing contributors to language-specific submodule repos.

Clone with submodules to access all language solutions: git clone --recursive https://github.com/careercup/CtCI-6th-Edition.git. For Java-only: git clone https://github.com/careercup/CtCI-6th-Edition.git. No build dependencies—Java files compile standalone with standard javac.

Daily commands: Compile individual files with javac Q1_01_Is_Unique/QuestionA.java or use Eclipse/IntelliJ (project is configured for both via .project and .classpath). Execute Tester.java files: java -cp . Tester to validate solutions against test cases.

• Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/QuestionA.java — First fundamental problem in the repository demonstrating string uniqueness validation; establishes the pattern for all subsequent question implementations.
• Java/Ch 02. Linked Lists/Q2_01_Remove_Dups/QuestionA.java — Core linked list data structure implementation; all linked list solutions depend on understanding this foundation.
• Java/Ch 03. Stacks and Queues/Introduction/MyStack.java — Reference stack implementation used throughout the stacks and queues chapter; essential for understanding all stack-based solutions.
• Java/Ch 03. Stacks and Queues/Introduction/MyQueue.java — Reference queue implementation; foundational abstraction for queue-based problems and queue via stacks solution.
• Java/Ch 04. Trees and Graphs/Introduction/Traversals.java — Tree traversal patterns (BFS, DFS) that are fundamental to all tree and graph problems in the repository.
• Java/Ch 04. Trees and Graphs/Q4_01_Route_Between_Nodes/Graph.java — Graph data structure implementation; critical for understanding all graph-based interview problems.
• README.md — Explains the repository structure, cloning procedure, and contribution workflow; must be read first by all contributors.

• Problem Question Classes (QuestionA/B/C.java) (Java) — Implement specific algorithmic solutions to interview problems with varying time/space trade-offs
  • Failure mode: Incorrect algorithm logic leads to wrong output or fails edge cases; impacts candidate confidence during interview prep
• Data Structure Implementations (MyStack, MyQueue, Graph.java) (Java generics, linked lists) — Provide reusable, interview-style data structure implementations that problems depend on
  • Failure mode: Bugs in core data structures cascade to all solutions; candidates memorize incorrect implementations
• Tester Classes — Validate solutions with test cases and demonstrate correct usage; enable side-

Add a new chapter with problems

1. Create new chapter directory following naming convention: Java/Ch XX. Topic Name (Java/Ch 05. Example Topic/)
2. For each problem, create question directory: QX_YY_Problem_Name (Java/Ch 05. Example Topic/Q5_01_Example_Problem/)
3. Implement multiple solution approaches (QuestionA.java, QuestionB.java) with comments explaining trade-offs (Java/Ch 05. Example Topic/Q5_01_Example_Problem/QuestionA.java)
4. Create Tester.java with main method demonstrating all approaches with test cases (Java/Ch 05. Example Topic/Q5_01_Example_Problem/Tester.java)

Add alternative solution approach to existing problem

1. Navigate to problem directory (e.g., Q1_01_Is_Unique) and identify existing QuestionA.java (Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/)
2. Create new QuestionC.java (or next letter) implementing alternative algorithm (Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/QuestionC.java)
3. Document time/space complexity trade-offs in comments and update or create Tester.java (Java/Ch 01. Arrays and Strings/Q1_01_Is_Unique/Tester.java)

Add solutions for new programming language

1. Create language-specific submodule repository following careercup/CtCI-6th-Edition-[Language] naming (.gitmodules)
2. Mirror chapter structure from Java directory: Ch 01, Ch 02, etc. with problem directories ([LanguageDirectory]/Ch 01. Arrays and Strings/Q1_01_Is_Unique/)
3. Include appropriate build/test files for language ecosystem (pom.xml, package.json, Cargo.toml, etc.) ([LanguageDirectory]/build.config)
4. Submit pull request referencing new submodule in .gitmodules with clear language specification (.gitmodules)

• Java — Primary language for the canonical solutions directly from Cracking the Coding Interview 6th Edition; widely used in technical interviews
• Git Submodules — Enables community-contributed solutions in multiple languages while maintaining single source of truth for Java solutions
• Multiple implementation approaches (A, B, C variants) — Teaches interview candidates to recognize and compare algorithmic trade-offs (time vs space, readability vs performance)

• Solutions organized by book chapter and problem number rather than algorithm type

  • Why: Mirrors the physical book structure for candidates studying from the text
  • Consequence: Requires readers to navigate across chapters to see patterns (e.g., all two-pointer solutions)

• Each problem has multiple solution files (QuestionA, B, C) rather than a single optimized version

  • Why: Demonstrates progression from naive to optimal solutions, teaching problem-solving methodology
  • Consequence: Increases file count and can be overwhelming; requires discipline to understand which approach to use

• Community-contributed solutions in separate submodule repos

  • Why: Decouples language-specific maintenance and allows independent contribution workflows
  • Consequence: Requires --recursive clone and increases cognitive load; contributions need coordination across multiple repos

• Not a runnable interview simulator or web platform
• Not a competitive programming judge with automated grading
• Not a real-time collaborative interview environment
• Not language-agnostic (Java solutions are canonical; others are community-maintained)
• Not a teaching platform with narrative tutorials (solutions without explanatory prose)

No external build dependencies or complex setup, but beware: (1) Eclipse/IntelliJ projects require proper .classpath/.project configuration—IDEs may need to rebuild indexes; (2) Git submodules require --recursive flag on clone or manual git submodule update --init --recursive—partial clones will miss non-Java languages; (3) Some Tester.java files use System.out.println without assertions, so test failures may be silent if not carefully reviewed; (4) File paths contain spaces (e.g., 'Ch 01. Arrays and Strings'), which can cause shell command issues if not quoted.

• Time-Space Trade-off (QuestionA vs. QuestionB patterns) — Every problem in this repo shows multiple solutions with different Big O trade-offs (e.g., HashSet O(n) space vs. sorting O(1) space); understanding when to optimize for time vs. memory is core to interview success
• In-place algorithms (rotation, zero matrix, string compression) — Multiple problems (Q1_07_Rotate_Matrix, Q1_08_Zero_Matrix) focus on modifying input without extra data structures; critical constraint in embedded systems and interview problems testing deep understanding
• Two-pointer technique (linked lists, palindromes) — Appears repeatedly in Ch 02 (Linked Lists) and string problems; elegant pattern for solving array/list problems in linear time with minimal space—essential interview technique
• Bit manipulation (parity, power of two checks) — Chapter on bit problems (implied by Big O examples) uses bitwise operators for elegant solutions; showing comfort with &, |, ^, >> is valued in interviews for systems-level thinking
• Hash tables as interview optimization tool — Dominant pattern across Q1_01, Q1_04, Q1_05—converting naive O(n²) brute-force to O(n) via HashMap; demonstrates practical algorithm optimization mindset expected in interviews
• Recursion with memoization (Big O examples reference dynamic programming) — While not heavily featured in provided file list, the Big O section hints at recursive problem optimization; CtCI tree/graph chapters (not shown) build on this foundation for interview prep
• Character encoding and Unicode (URLify, string problems) — Q1_03_URLify requires understanding ASCII/Unicode encoding and space handling in strings; practical knowledge needed for real systems beyond algorithmic thinking

• donnemartin/system-design-primer — Companion resource for interview prep; covers system design and architecture patterns beyond coding puzzles, used by same audience preparing for senior/FAANG roles
• careercup/CtCI-6th-Edition-Python — Official language-specific submodule repo referenced in .gitmodules; contains equivalent solutions translated to Python for candidates preferring that language
• williamfiset/Algorithms — Comprehensive algorithm visualizations and explanations; complementary deep-dive for learners wanting to understand the theory behind CtCI solutions
• trekhleb/javascript-algorithms — JavaScript equivalent of CtCI with animated explanations; targets web developers preparing interviews or learning data structures in their primary language
• MaximAbramchuck/awesome-interview-questions — Curated list of interview questions and resources across companies; provides context on which CtCI problems are most frequently asked in real interviews

To work on one of these in Claude Code or Cursor, paste: Implement the "<title>" PR idea from CLAUDE.md, working through the checklist as the task list.

Add comprehensive unit tests for Chapter 2 (Linked Lists) solutions

The Linked Lists directory has multiple implementations (QuestionA, QuestionB, QuestionC variants) but only some questions have Tester.java files. Q2_02_Return_Kth_To_Last contains a misplaced QuestionB.cpp (C++ file in Java directory) and inconsistent test coverage across variants. A unified JUnit test suite would validate all implementations and catch regressions.

• [ ] Create Java/Ch 02. Linked Lists/LinkedListTestSuite.java with JUnit tests
• [ ] Remove or relocate Java/Ch 02. Linked Lists/Q2_02_Return_Kth_To_Last/QuestionB.cpp to appropriate language directory
• [ ] Add tests covering all variants (A, B, C, D) for Q2_02_Return_Kth_To_Last
• [ ] Add test cases for Q2_03_Delete_Middle_Node and Q2_07_Intersection which lack Tester.java files
• [ ] Ensure edge cases are covered (empty lists, single nodes, null inputs)

Add GitHub Actions CI workflow for Java solutions compilation and testing

With 60+ Java question files across multiple chapters, there's no automated way to verify that code compiles or passes tests on pull requests. This increases the risk of breaking changes slipping through from community contributions. A CI workflow would catch compilation errors and test failures before merge.

• [ ] Create .github/workflows/java-ci.yml GitHub Actions workflow
• [ ] Configure Maven or Gradle build (infer from .classpath and .project files)
• [ ] Add compilation step for all Java source files in Java/ directory
• [ ] Add test execution step for all existing Tester.java and unit test files
• [ ] Set workflow to trigger on pull requests and commits to main branches

Create LinkedList and Node utility classes to reduce code duplication across questions

Multiple questions in Ch 02 (Q2_01 through Q2_08) appear to redefine LinkedList node structures and basic operations. The directory has Introduction/MyStack.java and Introduction/MyQueue.java but no LinkedList.java. Extracting a shared LinkedList implementation with Node inner class would reduce duplication, improve maintainability, and make solutions more consistent.

• [ ] Create Java/Ch 02. Linked Lists/Introduction/LinkedList.java with Node inner class
• [ ] Define standard methods: append(), deleteNode(), printList(), getKthToLast()
• [ ] Refactor Q2_01_Remove_Dups, Q2_02_Return_Kth_To_Last, Q2_03_Delete_Middle_Node to use shared LinkedList
• [ ] Update Tester.java files to use the common LinkedList utility
• [ ] Verify all existing tests still pass with refactored code

• Add JUnit test framework to replace manual Tester.java validation: convert 10-15 problem folders to use @Test annotations and AssertJ for clearer test structure and CI integration
• Document Big O complexity in JavaDoc comments: many QuestionA/B files lack explicit @complexity tags; add O(time) and O(space) tags to method headers across all Chapter 2 (Linked Lists) problems
• Create a test harness runner: write a TestRunner.java in the Java root that discovers and executes all Tester.java files, providing a unified test report (currently each problem must be run individually)

This is an educational repository containing coding interview solutions with minimal security risks. The codebase consists of Java solutions for the 'Cracking the Coding Interview' book and does not appear to be a production application. No critical vulnerabilities were identified. The main observations are: (1) No dependency management files (pom.xml, build.gradle) were provided for analysis; (2) No hardcoded secrets or credentials detected in file structure; (3) No web frameworks, databases, or network I/O patterns that would introduce injection risks; (4) No Docker configuration files present; (5) Code appears to be algorithmic implementations without security-sensitive operations. The repository is a safe educational resource with typical coding interview problem solutions in Java.

LLM-derived; treat as a starting point, not a security audit.

• Open issues — current backlog
• Recent PRs — what's actively shipping
• Source on GitHub

Generated by RepoPilot. Verdict based on maintenance signals — see the live page for receipts. Re-run on a new commit to refresh.