InterviewAlgorithms

Kotlin solutions to 40+ classic data structure & algorithm interview problems — curated from real FAANG, Stripe, LinkedIn and LeetCode rounds.

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InterviewAlgorithms is a hand-picked collection of Kotlin solutions to data structures and algorithms problems frequently asked in software engineering interviews at companies like Google, Meta, Amazon, LinkedIn, Stripe and Microsoft. Every file is a self-contained, runnable .kt source with a main function, an explanation of the problem, the approach, and the time/space complexity — perfect for Kotlin coding interview prep, LeetCode practice, or refreshing your DSA fundamentals.

If you are searching for Kotlin LeetCode solutions, Kotlin DSA examples, or a FAANG interview prep repo written in idiomatic Kotlin instead of Java or Python — you're in the right place.

Why Kotlin? Most interview-prep repos are written in Python, Java, or C++. Kotlin gives you the same JVM performance with cleaner, more expressive syntax — a huge time-saver in a 45-minute live coding round.

• 42 problems spanning arrays, strings, trees, graphs, dynamic programming, heaps, system design and more
• Idiomatic Kotlin — uses data class, extension functions, let, also, sealed classes, and standard collections
• Real interview attribution — many problems include the company that asked them and a link to the source (LeetCode, Prepfully, etc.)
• Complexity annotations — every solution documents Big-O time and space
• Multiple approaches — brute-force vs. optimized side-by-side where it matters (see TwoSum.kt)
• Zero dependencies — pure Kotlin standard library, runs on any JVM

• JDK 17 or newer
• Kotlin compiler 2.0+ (or just open the folder in IntelliJ IDEA)

git clone https://github.com/AliAzaz/InterviewAlgorithms.git
cd InterviewAlgorithms

# Compile and run any .kt file
kotlinc TwoSum.kt -include-runtime -d TwoSum.jar
java -jar TwoSum.jar

kotlinc -script TwoSum.kts   # rename .kt to .kts to script-run

1. File → Open → InterviewAlgorithms
2. IntelliJ will detect Kotlin and configure the JDK
3. Click the green ▶ next to any main function

InterviewAlgorithms/
├── banner.svg
├── README.md
├── *.kt                    # 39 problems at the repo root
├── intersection/
│   └── FindIntersection.kt
└── palindrome/
    ├── Palindrome_Integer.kt
    └── Palindrome_String.kt

Each .kt file is independent and self-contained — it has its own main function and can be compiled and run on its own without touching the rest of the repo.

Pull requests are very welcome. To keep the repo readable and useful for other interview candidates, please follow these guidelines.

1. Fork the repo and create a branch: git checkout -b add/<problem-name>
2. One problem per file, named in PascalCase.kt (e.g., LongestPalindrome.kt)
3. Place general problems at the repo root; group related variants in a subfolder (see palindrome/)
4. Start the file with a comment block:

   /*
    * Problem: <one-line description, plus LeetCode # if applicable>
    * Asked at: <company / source link, optional>
    * Approach: <one or two sentences>
    * Complexity: O(...) time · O(...) space
    */

5. Include a main() function with at least one example call so kotlinc <file>.kt -include-runtime -d <file>.jar && java -jar <file>.jar produces visible output
6. Open the PR with a short description and the LeetCode (or other) link

Found a bug or a cleaner solution? Open an issue or send a PR — both are appreciated.

kotlinc TwoSum.kt -include-runtime -d TwoSum.jar && java -jar TwoSum.jar

• Add JUnit/Kotest test suites per problem
• Add Gradle wrapper for one-command runs (./gradlew run -PmainClass=TwoSumKt)
• Add concurrency / coroutines section (producer-consumer, async pipelines)
• Add Kotlin Multiplatform variants for select problems
• GitHub Actions CI to compile every .kt on push

Released under the MIT License. You are free to use, modify and distribute the code for any purpose, including commercial use, with attribution.

Maintained by Ali Azaz. If this repo helped you land an interview, leave a ⭐ — it helps others discover it.