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HackerRankChallenges

★ 5 Open GitHub ↗

Solving hackerrank.com challenges for fun and world peace.

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# Hacker Rank Challenges

Playing with HackerRank challenges ([my profile](https://www.hackerrank.com/EvilNerdyOwl)) for fun, but also to stay
sharp and brush up on Computer Science fundamentals that so frequently pop up in FAANG style tech interviews. Solutions
are coded in Java 8 and pass all available tests to earn full points.

Each solution's `Result.java` class comes with a corresponding set of unit tests.
Using [JUnit 5](https://junit.org/junit5/docs/current/user-guide/) along with [AssertJ](https://assertj.github.io/doc/)
library for its convenient and fluent assertions. Test method names follow naming standard as
outlined [here](https://osherove.com/blog/2005/4/3/naming-standards-for-unit-tests.html).

# Problems

Total problems solved: 73

## Algorithms

| Category | Problem | Difficulty | Solution |
| --- | --- |:---:| --- |
| __Implementation (18):__ | | | | 
| | [Angry Professor](https://www.hackerrank.com/challenges/angry-professor)| Easy | [Result](src/main/java/hackrank/algorithm/implement/angryprof/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/angryprof/ResultTest.java) |
| | [Sherlock and The Beast](https://www.hackerrank.com/challenges/sherlock-and-the-beast)| Easy | [Result](src/main/java/hackrank/algorithm/implement/sherlock/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/sherlock/ResultTest.java) |
| | [Utopian Tree](https://www.hackerrank.com/challenges/utopian-tree)| Easy | [Result](src/main/java/hackrank/algorithm/implement/utopian/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/utopian/ResultTest.java) |
| | [Find Digits](https://www.hackerrank.com/challenges/find-digits)| Easy | [Result](src/main/java/hackrank/algorithm/implement/digit/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/digit/ResultTest.java) |
| | [Sherlock and Squares](https://www.hackerrank.com/challenges/sherlock-and-squares) | Easy | [Result](src/main/java/hackrank/algorithm/implement/squares/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/squares/ResultTest.java) |
| | [Service Lane](https://www.hackerrank.com/challenges/service-lane)| Easy | [Result](src/main/java/hackrank/algorithm/implement/lane/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/lane/ResultTest.java) |
| | [Bigger is Greater](https://www.hackerrank.com/challenges/bigger-is-greater) | Medium | [Result](src/main/java/hackrank/algorithm/implement/bigger/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/bigger/ResultTest.java) |
| | [Cut the Sticks](https://www.hackerrank.com/challenges/cut-the-sticks)| Easy | [Result](src/main/java/hackrank/algorithm/implement/stick/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/stick/ResultTest.java) |
| | [Chocolate Feast](https://www.hackerrank.com/challenges/chocolate-feast)| Easy | [Result](src/main/java/hackrank/algorithm/implement/chocolate/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/chocolate/ResultTest.java) |
| | [Caesar Cipher](https://www.hackerrank.com/challenges/caesar-cipher-1) | Easy | [Result](src/main/java/hackrank/algorithm/implement/caesar/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/caesar/ResultTest.java) |
| | [Grid Search](https://www.hackerrank.com/challenges/the-grid-search)| Medium | [Result](src/main/java/hackrank/algorithm/implement/grid/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/grid/ResultTest.java) |
| | [Cavity Map](https://www.hackerrank.com/challenges/cavity-map)| Easy | [Result](src/main/java/hackrank/algorithm/implement/cavity/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/cavity/ResultTest.java) |
| | [Manasa and Stones](https://www.hackerrank.com/challenges/manasa-and-stones) | Easy | [Result](src/main/java/hackrank/algorithm/implement/stones/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/stones/ResultTest.java) |
| | [Library Fine](https://www.hackerrank.com/challenges/library-fine) | Easy | [Result](src/main/java/hackrank/algorithm/implement/fine/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/fine/ResultTest.java) |
| | [ACM ICPC Team](https://www.hackerrank.com/challenges/acm-icpc-team) | Easy | [Result](src/main/java/hackrank/algorithm/implement/team/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/team/ResultTest.java) |
| | [Extra Long Factorial](https://www.hackerrank.com/challenges/extra-long-factorials) | Medium | [Result](src/main/java/hackrank/algorithm/implement/factorial/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/factorial/ResultTest.java) |
| | [Taum and B'day Challenge](https://www.hackerrank.com/challenges/taum-and-bday) | Easy | [Result](src/main/java/hackrank/algorithm/implement/bday/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/bday/ResultTest.java) |
| | [Time in Words](https://www.hackerrank.com/challenges/the-time-in-words) | Medium | [Result](src/main/java/hackrank/algorithm/implement/time/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/time/ResultTest.java) |
| | [Matrix Layer Rotation](https://www.hackerrank.com/challenges/matrix-rotation-algo) | Hard | [Result](src/main/java/hackrank/algorithm/implement/rotate/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/implement/rotate/ResultTest.java) |
| | | | |
| __Strings (11):__ | | | |
| | [Funny String](https://www.hackerrank.com/challenges/funny-string) | Easy | [Result](src/main/java/hackrank/algorithm/string/funny/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/funny/ResultTest.java) |
| | [Pangrams](https://www.hackerrank.com/challenges/pangrams) | Easy | [Result](src/main/java/hackrank/algorithm/string/pangram/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/pangram/ResultTest.java) |
| | [Alternating Characters](https://www.hackerrank.com/challenges/alternating-characters) | Easy | [Result](src/main/java/hackrank/algorithm/string/alternate/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/alternate/ResultTest.java) |
| | [Two Strings](https://www.hackerrank.com/challenges/two-strings) | Easy | [Result](src/main/java/hackrank/algorithm/string/two/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/two/ResultTest.java) |
| | [Sherlock and Anagrams](https://www.hackerrank.com/challenges/sherlock-and-anagrams) | Medium | [Result](src/main/java/hackrank/algorithm/string/shergram/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/shergram/ResultTest.java) |
| | [Game of Thrones](https://www.hackerrank.com/challenges/game-of-thrones) | Easy | [Result](src/main/java/hackrank/algorithm/string/thrones/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/thrones/ResultTest.java) |
| | [Gemstones](https://www.hackerrank.com/challenges/gem-stones) | Easy | [Result](src/main/java/hackrank/algorithm/string/gems/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/gems/ResultTest.java) |
| | [Making Anagrams](https://www.hackerrank.com/challenges/making-anagrams) | Easy | [Result](src/main/java/hackrank/algorithm/string/mkanagram/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/mkanagram/ResultTest.java) |
| | [Anagram](https://www.hackerrank.com/challenges/anagram) | Easy | [Result](src/main/java/hackrank/algorithm/string/anagram/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/anagram/ResultTest.java) |
| | [Palindrome Index](https://www.hackerrank.com/challenges/palindrome-index) | Easy | [Result](src/main/java/hackrank/algorithm/string/palindrome/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/palindrome/ResultTest.java) |
| | [Common Child](https://www.hackerrank.com/challenges/common-child) | Medium | [Result](src/main/java/hackrank/algorithm/string/child/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/child/ResultTest.java) |
| | [Sherlock and the Valid String](https://www.hackerrank.com/challenges/sherlock-and-valid-string) | Medium | [Result](src/main/java/hackrank/algorithm/string/sherlock/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/string/sherlock/ResultTest.java) |
| | | | | 
| __Bit Manipulation (4):__ | | | | 
| | [Lonely Integer](https://www.hackerrank.com/challenges/lonely-integer) | Easy | [Result](src/main/java/hackrank/algorithm/bit/lonely/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/bit/lonely/ResultTest.java) |
| | [Maximizing XOR](https://www.hackerrank.com/challenges/maximizing-xor) | Easy | [Result](src/main/java/hackrank/algorithm/bit/maxxor/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/bit/maxxor/ResultTest.java) |
| | [Flipping Bits](https://www.hackerrank.com/challenges/flipping-bits) | Easy | [Result](src/main/java/hackrank/algorithm/bit/flip/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/bit/flip/ResultTest.java) |
| | [Sansa and XOR](https://www.hackerrank.com/challenges/sansa-and-xor) | Medium | [Result](src/main/java/hackrank/algorithm/bit/sansa/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/bit/sansa/ResultTest.java) |
| | | | | 
| __Sorting (7):__ | | | |
| | [Insertion Sort Part 1](https://www.hackerrank.com/challenges/insertionsort1) | Easy | [Result](src/main/java/hackrank/algorithm/sort/insert1/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/insert1/ResultTest.java) |
| | [Insertion Sort Part 2](https://www.hackerrank.com/challenges/insertionsort2) | Easy | [Result](src/main/java/hackrank/algorithm/sort/insert2/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/insert2/ResultTest.java) |
| | [Insertion Sort Running Time](https://www.hackerrank.com/challenges/runningtime) | Easy | [Result](src/main/java/hackrank/algorithm/sort/insertrun/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/insertrun/ResultTest.java) |
| | [Quicksort Part 1](https://www.hackerrank.com/challenges/quicksort2) | Easy | [Result](src/main/java/hackrank/algorithm/sort/quick/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/quick/ResultTest.java) |
| | [Quicksort Part 2](https://www.hackerrank.com/challenges/quicksort3) | Medium | [Result](src/main/java/hackrank/algorithm/sort/quickinplace/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/quickinplace/ResultTest.java) |
| | [Counting Sort Part 1](https://www.hackerrank.com/challenges/countingsort1) | Easy | [Result](src/main/java/hackrank/algorithm/sort/count1/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/count1/ResultTest.java) |
| | [Counting Sort Part 2](https://www.hackerrank.com/challenges/countingsort2) | Easy | [Result](src/main/java/hackrank/algorithm/sort/count2/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/sort/count2/ResultTest.java) |
| | | | | 
| __Dynamic Programming (1):__ | | | |
| | [The Maximum Subarray](https://www.hackerrank.com/challenges/maxsubarray) | Medium | [Result](src/main/java/hackrank/algorithm/dynamic/maxsub/Result.java) - [Unit Test](src/test/java/hackrank/algorithm/dynamic/maxsub/ResultTest.java) |

## Data Structures

| Category | Problem | Difficulty | Solution |
| --- | --- |:---:| --- |
| __Arrays (1):__ | | | |
| | [Sparse Arrays](https://www.hackerrank.com/challenges/sparse-arrays) | Medium | [Result](src/main/java/hackrank/datastruct/array/sparse/Result.java) - [Unit Test](src/test/java/hackrank/datastruct/array/sparse/ResultTest.java) |
| | | | | 
| __Heap (1):__ | | | | 
| | [Find the Running Median](https://www.hackerrank.com/challenges/find-the-running-median) | Hard | [Result](src/main/java/hackrank/datastruct/heap/runningmedian/Result.java) - [Unit Test](src/test/java/hackrank/datastruct/heap/runningmedian/ResultTest.java) |

---

# Solutions (Old Format)

TODO: Convert each problem to new format and add unit tests.

## Algorithms

| Category | Name | Difficulty | Problem | Solution |
| --- | --- |:---:| --- | --- |
| __Sorting (2):__ | | | | |
| | Counting Sort Part 3 | Easy | [Problem](https://www.hackerrank.com/challenges/countingsort3) | [Solution](src/main/java/hackrank/algorithm/sort/count3/Solution.java) |
| | Counting Sort Part 4 | Moderate | [Problem](https://www.hackerrank.com/challenges/countingsort4) | [Solution](src/main/java/hackrank/algorithm/sort/count4/Solution.java) |
| | | | |
| __Search (6):__ | | | | | 
| | Sherlock and Array | Easy | [Problem](https://www.hackerrank.com/challenges/sherlock-and-array) | [Solution](src/main/java/hackrank/algorithm/search/sherlock/Solution.java) |
| | Ice Cream Parlor | Easy | [Problem](https://www.hackerrank.com/challenges/icecream-parlor) | [Solution](src/main/java/hackrank/algorithm/search/icecream/Solution.java) |  
| | Missing Numbers | Moderate | [Problem](https://www.hackerrank.com/challenges/missing-numbers) | [Solution](src/main/java/hackrank/algorithm/search/missing/Solution.java) |
| | Connected Cells | Moderate | [Problem](https://www.hackerrank.com/challenges/connected-cell-in-a-grid) | [Solution](src/main/java/hackrank/algorithm/search/connected/Solution.java) |
| | Count Luck | Easy | [Problem](https://www.hackerrank.com/challenges/count-luck) | [Solution](src/main/java/hackrank/algorithm/search/luck/Solution.java) |
| | Cut the Tree | Moderate | [Problem](https://www.hackerrank.com/challenges/cut-the-tree) | [Solution](src/main/java/hackrank/algorithm/search/cuttree/Solution.java) |
| | | | |
| __Graph Theory (7):__ | | | | | 
| | Breadth Shortest Reach | Moderate | [Problem](https://www.hackerrank.com/challenges/bfsshortreach) | [Solution](src/main/java/hackrank/algorithm/graph/bfsreach/Solution.java) |
| | Dijkstra Shortest Reach | Difficult | [Problem](https://www.hackerrank.com/challenges/dijkstrashortreach) | [Solution](src/main/java/hackrank/algorithm/graph/dijkstrareach/Solution.java) |
| | Prim's Special Subtree | Moderate | [Problem](https://www.hackerrank.com/challenges/primsmstsub) | [Solution](src/main/java/hackrank/algorithm/graph/primsubtree/Solution.java) |  
| | Kruskal's Really Special Subtree | Difficult | [Problem](https://www.hackerrank.com/challenges/kruskalmstrsub) | [Solution](src/main/java/hackrank/algorithm/graph/kruskalmst/Solution.java) |
| | Even Tree | Moderate | [Problem](https://www.hackerrank.com/challenges/even-tree) | [Solution](src/main/java/hackrank/algorithm/graph/eventree/Solution.java) |
| | Journey to the Moon | Moderate | [Problem](https://www.hackerrank.com/challenges/journey-to-the-moon) | [Solution](src/main/java/hackrank/algorithm/graph/moon/Solution.java) |  
| | Snakes and Ladders | Easy | [Problem](https://www.hackerrank.com/challenges/the-quickest-way-up) | [Solution](src/main/java/hackrank/algorithm/graph/snake/Solution.java) |
| | | | |
| __Greedy (9):__ | | | | |
| | Grid Challenge | Easy | [Problem](https://www.hackerrank.com/challenges/grid-challenge) | [Solution](src/main/java/hackrank/algorithm/greedy/grid/Solution.java) |
| | Jim and the Orders | Easy | [Problem](https://www.hackerrank.com/challenges/jim-and-the-orders) | [Solution](src/main/java/hackrank/algorithm/greedy/jimorder/Solution.java) |   
| | Mark and Toys | Easy | [Problem](https://www.hackerrank.com/challenges/mark-and-toys) | [Solution](src/main/java/hackrank/algorithm/greedy/toys/Solution.java) |
| | Two Arrays | Easy | [Problem](https://www.hackerrank.com/challenges/two-arrays) | [Solution](src/main/java/hackrank/algorithm/greedy/arrays/Solution.java) |
| | Priyanka and Toys | Easy | [Problem](https://www.hackerrank.com/challenges/priyanka-and-toys) | [Solution](src/main/java/hackrank/algorithm/greedy/priyanka/Solution.java) |
| | Largest Permutation | Easy | [Problem](https://www.hackerrank.com/challenges/largest-permutation) | [Solution](src/main/java/hackrank/algorithm/greedy/permute/Solution.java) |
| | Flowers | Moderate | [Problem](https://www.hackerrank.com/challenges/flowers) | [Solution](src/main/java/hackrank/algorithm/greedy/flowers/Solution.java) |
| | Cutting Boards | Moderate | [Problem](https://www.hackerrank.com/challenges/board-cutting) | [Solution](src/main/java/hackrank/algorithm/greedy/boardcut/Solution.java) |
| | Max Min | Moderate | [Problem](https://www.hackerrank.com/challenges/angry-children) | [Solution](src/main/java/hackrank/algorithm/greedy/maxmin/Solution.java) |
| | | | |
| __Dynamic Programming (4):__ | | | | |
| | Fibonacci Modified | Moderate | [Problem](https://www.hackerrank.com/challenges/fibonacci-modified) | [Solution](src/main/java/hackrank/algorithm/dynamic/fibmod/Solution.java) |
| | Coin Change | Moderate | [Problem](https://www.hackerrank.com/challenges/coin-change) | [Solution](src/main/java/hackrank/algorithm/dynamic/coin/Solution.java) |
| | Candies | Moderate | [Problem](https://www.hackerrank.com/challenges/candies) | [Solution](src/main/java/hackrank/algorithm/dynamic/candy/Solution.java) |
| | Stock Maximize | Moderate | [Problem](https://www.hackerrank.com/challenges/stockmax) | [Solution](src/main/java/hackrank/algorithm/dynamic/maxstock/Solution.java) |

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