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Solutions of Hackerrank challenges in various languages - Scala, Java, Javascript, Ruby, ...

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# Hackerrank
Solutions of [Hackerrank](https://www.hackerrank.com) challenges in various languages.

*   [Project Euler+](#project-euler)
*   [Practice](#algorithms)
    *  [Algorithms](#algorithms)
    *  [Data Structures](#data-structures)
    *  [Mathematics](#mathematics)
    *  [Java](#java)
    *  [Functional Programming](#functional-programming)
    *  [Linux shell](#linux)
    *  [SQL](#sql)
    *  [Regex](#regex)

## Project Euler+

*   [Project Euler #1: Multiples of 3 and 5](http://pidanic.com/blog/hackerrank-project-euler-001-multiples-3-5/)
*   [Project Euler #2: Even Fibonacci numbers](http://pidanic.com/blog/hackerrank-project-euler-002-even-fibonacci-numbers/)
*   [Project Euler #3: Largest prime factor](http://pidanic.com/blog/hackerrank-project-euler-003-largest-prime-factor/)
*   [Project Euler #4: Largest palindrome product](http://pidanic.com/blog/hackerrank-project-euler-004-largest-palindrome-product/)
*   [Project Euler #5: Smallest multiple](http://pidanic.com/blog/hackerrank-project-euler-005-smallest-multiple/)
*   [Project Euler #6: Sum square difference](http://pidanic.com/blog/hackerrank-project-euler-006-sum-square-difference/)
*   [Project Euler #7: 10001st prime](http://pidanic.com/blog/hackerrank-project-euler-007-10001st-prime/)
*   [Project Euler #8: Largest product in a series](http://pidanic.com/blog/hackerrank-project-euler-008-largest-product-series/)
*   [Project Euler #9: Special Pythagorean triplet](http://pidanic.com/blog/hackerrank-project-euler-009-special-pythagorean-triplet/)
*   [Project Euler #10: Summation of primes](http://pidanic.com/blog/hackerrank-project-euler-010-summation-primes/)
*   [Project Euler #11: Largest product in a grid](http://pidanic.com/blog/hackerrank-project-euler-011-largest-product-grid/)
*   [Project Euler #12: Highly divisible triangular number](http://pidanic.com/blog/hackerrank-project-euler-012-highly-divisible-triangular-number/)
*   [Project Euler #13: Large sum](http://pidanic.com/blog/hackerrank-project-euler-013-large-sum/)
*   [Project Euler #14: Longest Collatz sequence](http://pidanic.com/blog/hackerrank-project-euler-014-longest-collatz-sequence/)
*   [Project Euler #15: Lattice paths](http://pidanic.com/blog/hackerrank-project-euler-015-lattice-paths/)
*   [Project Euler #16: Power digit sum](http://pidanic.com/blog/hackerrank-project-euler-016-power-digit-sum/)
*   [Project Euler #17: Number to Words](http://pidanic.com/blog/hackerrank-project-euler-017-number-words/)
*   [Project Euler #18: Maximum path sum I](http://pidanic.com/blog/hackerrank-project-euler-018-maximum-path-sum/)
*   [Project Euler #19: Counting Sundays](http://pidanic.com/blog/hackerrank-project-euler-019-counting-sundays/)
*   [Project Euler #20: Factorial digit sum](http://pidanic.com/blog/hackerrank-project-euler-020-factorial-digit-sum/)
*   [Project Euler #22: Names scores](http://pidanic.com/blog/hackerrank-project-euler-022-name-scores/)
*   [Project Euler #36: Double-base palindromes](http://pidanic.com/blog/hackerrank-project-euler-036-double-base-palindromes/)
*   [Project Euler #67: Maximum path sum II](http://pidanic.com/blog/hackerrank-project-euler-067-maximum-path-sum-ii/)

## Algorithms

#### Warmup

*   [[Easy] Solve me first (1 pt)](http://pidanic.com/blog/hackerrank-solve-me-first)
*   [[Easy] Simple Array Sum (10 pts)](http://pidanic.com/blog/hackerrank-simple-array-sum)
*   [[Easy] Staircase (10 pts)](http://pidanic.com/blog/hackerrank-staircase)
*   [[Easy] Diagonal Difference (10 pts)](http://pidanic.com/blog/hackerrank-diagonal-difference)
*   [[Easy] A Very Big Sum (10 pts)](http://pidanic.com/blog/hackerrank-a-very-big-sum)
*   [[Easy] Plus Minus (10 pts)](http://pidanic.com/blog/hackerrank-plus-minus)
*   [[Easy] Time Conversion (15 pts)](http://pidanic.com/blog/hackerrank-time-conversion)
*   [[Easy] Compare The Triples (10 pts)](http://pidanic.com/blog/hackerrank-compare-triplets/)
*   [[Easy] Circular Array Rotation (20 pts)](http://pidanic.com/blog/hackerrank-circular-array-rotation/)
*   [[Easy] Birthday Cake Candles (10 pts)](http://pidanic.com/en/blog/hackerrank-birthday-cake-candles/)

#### Implementation

*   [[Easy] Divisible Sum Pairs (10 pts)](http://pidanic.com/blog/hackerrank-divisible-sum-pairs/)
*   [[Easy] Sequence Equation (20 pts)](http://pidanic.com/en/blog/hackerrank-sequence-equation/)
*   [[Easy] Lisa's Workbook (30 pts)](http://pidanic.com/blog/hackerrank-lisas-workbook/)
*   [[Easy] Library Fine (15 pts)](http://pidanic.com/blog/hackerrank-library-fine)
*   [[Easy] Caesar Cipher (15 pts)](http://pidanic.com/blog/hackerrank-caesar-cipher)
*   [[Easy] Angry Professor (20 pts)](http://pidanic.com/blog/hackerrank-angry-professor/)
*   [[Medium] Extra long factorials (20 pts)](http://pidanic.com/blog/hackerrank-extra-long-factorials)
*   [[Easy] Service Lane (20 pts)](http://pidanic.com/blog/hackerrank-service-lane)
*   [[Easy] Utopian Tree (20 pts)](http://pidanic.com/blog/hackerrank-utopian-tree)
*   [[Easy] Chocolate Feast (25 pts)](http://pidanic.com/blog/hackerrank-chocolate-feast)
*   [[Easy] Modified Kaprekar Numbers (30 pts)](http://pidanic.com/blog/hackerrank-modified-kaprekar-numbers/)
*   [[Easy] Sherlock and Squares (20 pts)](http://pidanic.com/blog/hackerrank-sherlock-squares/)
*   [[Easy] Manasa and Stones (30 pts)](http://pidanic.com/blog/hackerrank-manasa-and-stones)
*   [[Easy] Cut the sticks (25 pts)](http://pidanic.com/blog/hackerrank-cut-sticks)
*   [[Easy] Find Digits (25 pts)](http://pidanic.com/blog/hackerrank-find-digits)
*   [[Easy] Cavity Map (30 pts)](http://pidanic.com/blog/hackerrank-cavity-map)
*   [[Easy] Sherlock and The Beast (30 pts)](http://pidanic.com/blog/hackerrank-sherlock-and-the-beast)
*   [[Medium] Encryption (30 pts)](http://pidanic.com/blog/hackerrank-encryption)
*   [[Easy] Strange Counter (30 pts)](http://pidanic.com/blog/hackerrank-strange-counter/)
*   [[Easy] Beautiful Triplets (20 pts)](http://pidanic.com/blog/hackerrank-beautiful-triplets)
*   [[Easy] Kangaroo (10 pts)](http://pidanic.com/blog/hackerrank-kangaroo)
*   [[Easy] Save the Prisoner! (15 pts)](http://pidanic.com/blog/hackerrank-save-prisoner)
*   [[Easy] Minumum Distances (20 pts)](http://pidanic.com/blog/hackerrank-minimum-distances)
*   [[Easy] Jumping on the Clouds (20 pts)](http://pidanic.com/blog/hackerrank-jumping-clouds)
*   [[Easy] Jumping on the Clouds: Revisited (15 pts)](http://pidanic.com/blog/hackerrank-jumping-clouds-revisited)
*   [[Easy] Sock Merchant (10 pts)](http://pidanic.com/blog/hackerrank-sock-merchant)
*   [[Easy] Repeated String (20 pts)](http://pidanic.com/blog/hackerrank-repeated-string/)
*   [[Easy] Equalize the Array (20 pts)](http://pidanic.com/blog/hackerrank-equalize-array/)
*   [[Easy] Viral Advertising (15 pts)](http://pidanic.com/blog/hackerrank-viral-advertising/ )
*   [[Easy] Apple and Orange (10 pts)](http://pidanic.com/blog/hackerrank-apple-orange/)
*   [[Easy] Mini-Max Sum (10 pts)](http://pidanic.com/blog/hackerrank-mini-max-sum/)
*   [[Easy] Bon Appétit (10 pts)](http://pidanic.com/blog/hackerrank-bon-appetit/ )
*   [[Easy] Beautiful Days at the Movies (15 pts)](http://pidanic.com/blog/hackerrank-beautiful-days-movies/)
*   [[Easy] Designer PDF Viewer (20 pts)](http://pidanic.com/blog/hackerrank-designer-pdf-viewer/)
*   [[Easy] Flatland Space Stations (25 pts)](http://pidanic.com/blog/hackerrank-flatland-space-stations/)
*   [[Easy] Grading Students (10 pts)](http://pidanic.com/blog/hackerrank-grading-students/)
*   [[Easy] Between Two Sets (10 pts)](http://pidanic.com/blog/hackerrank-two-sets/)
*   [[Easy] The Hurdle Race (15 pts)](http://pidanic.com/blog/hackerrank-hurdle-race/)
*   [[Easy] Taum and B'day (25 pts)](http://pidanic.com/en/blog/hackerrank-taum-bday/)
*   [[Easy] ACM ICPC Team (25 pts)](http://pidanic.com/en/blog/hackerrank-acm-icpc-team/)
*   [[Easy] Drawing Book (10 pts)](http://pidanic.com/en/blog/hackerrank-drawing-book/)
*   [[Easy] Day of the Programmer (15 pts)](http://pidanic.com/en/blog/hackerrank-day-programmer/)
*   [[Easy] Electronics Shop (15 pts)](http://pidanic.com/en/blog/hackerrank-electronics-shop/)
*   [[Easy] Migratory Birds (10 pts)](http://pidanic.com/en/blog/hackerrank-migratory-birds/)
*   [[Easy] Picking Numbers (20 pts)](http://pidanic.com/en/blog/hackerrank-picking-numbers/)
*   [[Easy] Birthday Chocolate (10 pts)](http://pidanic.com/en/blog/hackerrank-birthday-chocolate/)
*   [[Easy] Breaking the Records (10 pts)](http://pidanic.com/en/blog/hackerrank-breaking-records/)
*   [[Easy] Cats and a Mouse (15 pts)](http://pidanic.com/en/blog/hackerrank-cats-mouse/)
*   [[Easy] Counting Valleys (15 pts)](http://pidanic.com/en/blog/hackerrank-counting-valleys/)

#### Strings

*   [[Easy] Super Reduced String (10 pts)](http://pidanic.com/blog/hackerrank-super-reduced-string/ )
*   [[Easy] CamelCase (15 pts)](http://pidanic.com/blog/hackerrank-camelcase/ )
*   [[Easy] The Love-Letter Mystery (20 pts)](http://pidanic.com/blog/hackerrank-the-love-letter-mystery)
*   [[Easy] Alternating Characters (20 pts)](http://pidanic.com/blog/hackerrank-alternating-characters)
*   [[Easy] Gemstones (20 pts)](http://pidanic.com/blog/hackerrank-gemstones)
*   [[Easy] Pangrams (20 pts)](http://pidanic.com/blog/hackerrank-pangrams)
*   [[Easy] Game of Thrones - I (30 pts)](http://pidanic.com/blog/hackerrank-game-of-thrones-i)
*   [[Easy] Funny String (25 pts)](http://pidanic.com/blog/hackerrank-funny-string)
*   [[Easy] Anagram (25 pts)](http://pidanic.com/blog/hackerrank-anagram)
*   [[Easy] Beautiful Binary String (20 pts)](http://pidanic.com/blog/hackerrank-beautiful-binary-string)
*   [[Easy] Mars Exploration (15 pts)](http://pidanic.com/blog/hackerrank-mars-exploration)
*   [[Easy] String Construction (25 pts)](http://pidanic.com/blog/hackerrank-string-construction)
*   [[Easy] Weighted Uniform Strings (25 pts)](http://pidanic.com/en/blog/hackerrank-weighted-uniform-strings/)
*   [[Easy] Two Characters (20 pts)](http://pidanic.com/en/blog/hackerrank-two-characters/ )
*   [[Easy] Separate the Numbers (20 pts)](http://pidanic.com/en/blog/hackerrank-separate-numbers/)
*   [[Easy] Making Anagrams (30 pts)](http://pidanic.com/en/blog/hackerrank-making-anagrams/)
*   [[Medium] Sherlock and Anagrams (50 pts)](http://pidanic.com/en/blog/hackerrank-sherlock-anagrams/)
*   [[Difficult] Common Child (60 pts)](http://pidanic.com/blog/hackerrank-common-child)

#### Sorting

*   [[Easy] Intro to Tutorial Challenges (30 pts)](http://pidanic.com/blog/hackerrank-intro-to-tutorial-challenges)
*   [[Easy] Insertion Sort - Part 1 (30 pts)](http://pidanic.com/blog/hackerrank-insertion-sort-part-1)
*   [[Easy] Insertion Sort - Part 2 (30 pts)](http://pidanic.com/blog/hackerrank-insertion-sort-part-2)
*   [[Easy] Counting Sort 1 (30 pts)](http://pidanic.com/en/blog/hackerrank-counting-sort-1/)
*   [[Easy] Closest Numbers (35 pts)](http://pidanic.com/blog/hackerrank-closest-numbers)

#### Search

*   [[Easy] Ice Cream Parlor (30 pts)](http://pidanic.com/blog/hackerrank-ice-cream-parlor)
*   [[Medium] Missing Numbers (45 pts)](http://pidanic.com/blog/hackerrank-missing-numbers)
*   [[Medium] Pairs (40 pts)](http://pidanic.com/blog/hackerrank-pairs)

#### Graph Theory

*   [[Medium] Even Tree (50 pts)](http://pidanic.com/blog/hackerrank-even-tree)
*   [[Medium] Snakes and Ladders: The Quickest Way Up (50 pts)](http://pidanic.com/blog/hackerrank-snakes-and-ladders-the-quickest-way-up)

#### Greedy

*   [[Medium] Flowers (35 pts)](http://pidanic.com/blog/hackerrank-flowers)
*   [[Medium] Max Min (35 pts)](http://pidanic.com/blog/hackerrank-max-min)
*   [[Easy] Two Arrays (40 pts)](http://pidanic.com/blog/hackerrank-two-arrays)
*   [[Easy] Priyanka and Toys (30 pts)](http://pidanic.com/en/blog/hackerrank-priyanka-toys/)
*   [[Easy] Mark and Toys (35 pts)](http://pidanic.com/en/blog/hackerrank-mark-toys/)

#### Dynamic Programming

*   [[Easy] The Maximum Subarray (50 pts)](http://pidanic.com/blog/hackerrank-maximum-subarray/)

#### Bit Manipulation

*   [[Easy] Lonely Integer (20 pts)](http://pidanic.com/blog/hackerrank-lonely-integer)
*   [[Easy] Maximizing XOR (30 pts)](http://pidanic.com/blog/hackerrank-maximizing-xor)
*   [[Easy] Flipping Bits (40 pts)](http://pidanic.com/blog/hackerrank-flipping-bits)
*   [[Easy] Sum vs XOR (25 pts)](http://pidanic.com/blog/hackerrank-sum-vs-xor/)

## Data Structures

#### Arrays

*   [[Easy] Arrays- DS (10 pts)](http://pidanic.com/blog/hackerrank-arrays-ds)

#### Linked Lists

*   [[Easy] Print the Elements of a linked list (5 pts)](http://pidanic.com/blog/hackerrank-print-the-elements-of-a-linked-list)

## Mathematics

#### Fundamentals

*   [[Easy] Find Point (5 pts)](http://pidanic.com/blog/hackerrank-find-point)
*   [[Easy] Minimum Draws (5 pts)](http://pidanic.com/blog/hackerrank-minimum-draws)
*   [[Easy] Connecting Towns (10 pts)](http://pidanic.com/blog/hackerrank-connecting-towns)
*   [[Easy] Handshake (10 pts)](http://pidanic.com/blog/hackerrank-handshake)
*   [[Easy] Halloween Party (20 pts)](http://pidanic.com/blog/hackerrank-halloween-party)
*   [[Easy] Filling Jars (20 pts)](http://pidanic.com/blog/hackerrank-filling-jars)
*   [[Medium] Is Fibo (20 pts)](http://pidanic.com/blog/hackerrank-is-fibo)

#### Number Theory

*   [[Medium] Equations (60 pts)](http://pidanic.com/blog/hackerrank-equations)

#### Combinatorics

*   [[Expert] Building a List (40 pts)](http://pidanic.com/blog/hackerrank-building-a-list)
*   [[Easy] Picking Cards (50 pts)](http://pidanic.com/blog/hackerrank-picking-cards)
*   [[Medium] Consecutive Subsequences (50 pts)](http://pidanic.com/en/blog/hackerrank-consecutive-subsequences/)

#### Probability

*   [[Easy] B'day Gift (30 pts)](http://pidanic.com/blog/hackerrank-bday-gift)

## Java

#### Introduction

*   [[Easy] Welcome To Java! (3 pts)](http://pidanic.com/blog/hackerrank-welcome-to-java)
*   [[Easy] Java If-Else (10 pts)](http://pidanic.com/blog/hackerrank-java-if-else)
*   [[Easy] Java Stdin and Stdout 1 (5 pts)](http://pidanic.com/blog/hackerrank-java-stdin-and-stdout-1)
*   [[Easy] Java Stdin and Stdout 2 (10 pts)](http://pidanic.com/blog/hackerrank-java-stdin-stdout-ii/)
*   [[Easy] Java Output Formatting (10 pts)](http://pidanic.com/blog/hackerrank-java-output-formatting/)
*   [[Easy] Java Loops I (10 pts)](http://pidanic.com/blog/hackerrank-java-loops/)
*   [[Easy] Java Loops II (10 pts)](http://pidanic.com/blog/hackerrank-java-loops-ii/)
*   [[Easy] Java Datatypes (10 pts)](http://pidanic.com/blog/hackerrank-java-datatypes/)
*   [[Easy] Java End-of-file (10 pts)](http://pidanic.com/blog/hackerrank-java-end-file/)
*   [[Easy] Java Static Initializer Block (10 pts)](http://pidanic.com/blog/hackerrank-java-static-initializer-block/)
*   [[Easy] Java Int to String (10 pts)](http://pidanic.com/blog/hackerrank-java-int-string/)
*   [[Easy] Java Date and Time (15 pts)](http://pidanic.com/blog/hackerrank-java-date-time/)
*   [[Easy] Java Currency Formatter (15 pts)](http://pidanic.com/blog/hackerrank-java-currency-formatter/)

#### Strings

*   [[Easy] Java Strings Introduction (5 pts)](http://pidanic.com/blog/hackerrank-java-strings-introduction/ )

## SQL

#### Basic Select

*   [[Easy] Select All (10 pts)](http://pidanic.com/blog/hackerrank-select-all)
*   [[Easy] Revising the Select Query - 1 (10 pts)](http://pidanic.com/blog/hackerrank-revising-the-select-query-1)
*   [[Easy] Revising the Select Query - 2 (10 pts)](http://pidanic.com/blog/hackerrank-revising-the-select-query-2)
*   [[Easy] Select by ID (10 pts)](http://pidanic.com/blog/hackerrank-select-by-id)
*   [[Easy] Japanese Cities' Detail (10 pts)](http://pidanic.com/blog/hackerrank-japanese-cities-detail)
*   [[Easy] Japanese Cities' Names (10 pts)](http://pidanic.com/blog/hackerrank-japanese-cities-name)
*   [[Easy] Weather Observation Station 1 (15 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-1)
*   [[Easy] Weather Observation Station 3 (10 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-3)
*   [[Easy] Weather Observation Station 4 (10 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-4)
*   [[Medium] Weather Observation Station 5 (30 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-5)
*   [[Easy] Weather Observation Station 6 (10 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-6)
*   [[Easy] Weather Observation Station 7 (10 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-7)
*   [[Easy] Weather Observation Station 8 (15 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-8)
*   [[Easy] Weather Observation Station 9 (10 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-9)
*   [[Easy] Weather Observation Station 10 (10 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-10)
*   [[Easy] Weather Observation Station 11 (15 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-11)
*   [[Easy] Weather Observation Station 12 (15 pts)](http://pidanic.com/blog/hackerrank-weather-observation-station-12)
*   [[Medium] Higher Than 75 Marks (15 pts)](http://pidanic.com/blog/hackerrank-higher-than-75-marks)

## Linux Shell

#### Bash

*   [[Easy] Let's Echo (1 pt)](http://pidanic.com/blog/hackerrank-lets-echo)
*   [[Easy] Looping and Skipping (2 pts)](http://pidanic.com/blog/hackerrank-looping-and-skipping)
*   [[Easy] A Personalized Echo (1 pt)](http://pidanic.com/blog/hackerrank-a-personalized-echo)
*   [[Easy] Looping with Numbers (2 pts)](http://pidanic.com/blog/hackerrank-looping-with-numbers)
*   [[Easy] The World of Numbers (2 pts)](http://pidanic.com/blog/hackerrank-the-world-of-numbers)
*   [[Easy] Comparing Numbers (3 pts)](http://pidanic.com/blog/hackerrank-comparing-numbers)
*   [[Easy] Getting started with conditionals (3 pts)](http://pidanic.com/blog/hackerrank-getting-started-with-conditionals)

#### Text Processing

*   [[Easy] Cut #1 (1 pt)](http://pidanic.com/blog/hackerrank-cut-1)
*   [[Easy] Cut #2 (1 pt)](http://pidanic.com/blog/hackerrank-cut-2)
*   [[Easy] Head of a Text File #1 (2 pts)](http://pidanic.com/blog/hackerrank-head-of-a-text-file-1)
*   [[Easy] Head of a Text File #2 (2 pts)](http://pidanic.com/blog/hackerrank-head-of-a-text-file-2)
*   [[Easy] Tr' Command #1 (1 pt)](http://pidanic.com/blog/hackerrank-tr-command-1)
*   [[Easy] Sort Command #1 (1 pt)](http://pidanic.com/blog/hackerrank-sort-command-1)
*   [[Easy] Sort Command #2 (1 pt)](http://pidanic.com/blog/hackerrank-sort-command-2)
*   [[Easy] Tr' Command #2 (1 pt)](http://pidanic.com/blog/hackerrank-tr-command-2)

#### Grep Sed Awk

*   [[Easy] Grep' #1 (2 pts)](http://pidanic.com/blog/hackerrank-grep-1)
*   [[Easy] Grep' #2 (2 pts)](http://pidanic.com/blog/hackerrank-grep-2)

## Functional Programming

#### Introduction

*   [[Easy] Solve me first FP (3 pts)](http://pidanic.com/blog/hackerrank-solve-me-first-fp)
*   [[Easy] Lambda Calculus - Evaluating Expressions #1 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-evaluating-expressions-1)
*   [[Easy] Lambda Calculus - Evaluating Expressions #2 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-evaluating-expressions-2)
*   [[Easy] Lambda Calculus - Evaluating Expressions #3 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-evaluating-expressions-3)
*   [[Medium] Lambda Calculus - Evaluating Expressions #4 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-evaluating-expressions-4)
*   [[Medium] Lambda Calculus - Evaluating Expressions #5 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-evaluating-expressions-5)
*   [[Easy] Lambda Calculus - Reductions #1 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-reductions-1/)
*   [[Easy] Lambda Calculus - Reductions #2 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-reductions-2/)
*   [[Medium] Lambda Calculus - Reductions #3 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-reductions-3/)
*   [[Medium] Lambda Calculus - Reductions #4 (5 pts)](http://pidanic.com/blog/hackerrank-lambda-calculus-reductions-4/)
*   [[Easy] Hello World (5 pts)](http://pidanic.com/blog/hackerrank-hello-world)
*   [[Easy] Hello World N Times (5 pts)](http://pidanic.com/blog/hackerrank-hello-world-n-times)
*   [[Easy] List Replication (10 pts)](http://pidanic.com/blog/hackerrank-list-replication)
*   [[Easy] Filter Array (10 pts)](http://pidanic.com/blog/hackerrank-filter-array)
*   [[Easy] Update List (10 pts)](http://pidanic.com/blog/hackerrank-update-list)
*   [[Easy] List Length (10 pts)](http://pidanic.com/blog/hackerrank-list-length)
*   [[Easy] Array Of N Elements (10 pts)](http://pidanic.com/blog/hackerrank-array-of-n-elements)
*   [[Easy] Reverse a list (10 pts)](http://pidanic.com/blog/hackerrank-reverse-a-list)
*   [[Easy] Sum of odd elements (10 pts)](http://pidanic.com/blog/hackerrank-sum-of-odd-elements)
*   [[Easy] Filter positions in a list (10 pts)](http://pidanic.com/blog/hackerrank-filter-positions-in-a-list)
*   [[Easy] Evaluating e^x (20 pts)](http://pidanic.com/blog/hackerrank-evaluating-ex)
*   [[Easy] Area Under Curves and Volume of Revolving a Curve (30 pts)](http://pidanic.com/blog/hackerrank-area-curves-volume-revolving-curve )
*   [[Easy] Functions or Not (5 pts)](http://pidanic.com/blog/hackerrank-functions-not/ )
*   [[Easy] Compute the Perimeter of a Polygon (15 pts)](http://pidanic.com/bloghttp://pidanic.com/blog/hackerrank-compute-perimeter-polygon/ )
*   [[Easy] Compute the Area of a Polygon (20 pts)](http://pidanic.com/blog/hackerrank-compute-area-polygon/ )

#### Recursion

*   [[Easy] Computing the GCD (2 pts)](http://pidanic.com/blog/hackerrank-computing-the-gcd)
*   [[Easy] Fibonacci Numbers (2 pts)](http://pidanic.com/blog/hackerrank-fibonacci-numbers)
*   [[Easy] Pascal's Triangle (10 pts)](http://pidanic.com/blog/hackerrank-pascals-triangle)
*   [[Easy] String Mingling (20 pts)](http://pidanic.com/blog/hackerrank-string-mingling)
*   [[Easy] String-o-Permute (10 pts)](http://pidanic.com/blog/hackerrank-string-o-permute/ )
*   [[Easy] String Reductions (10 pts)](http://pidanic.com/blog/hackerrank-string-reductions)
*   [[Easy] Prefix Compression (10 pts)](http://pidanic.com/blog/hackerrank-prefix-compression)
*   [[Easy] Sequence full of colors (10 pts)](http://pidanic.com/blog/hackerrank-sequence-full-colors/)
*   [[Easy] String Compression (10 pts)](http://pidanic.com/en/blog/hackerrank-string-compression/)
*   [[Medium] Super Digit (20 pts)](http://pidanic.com/blog/hackerrank-super-digit/)

#### Ad Hoc

*   [[Easy] Remove Duplicates (10 pts)](http://pidanic.com/blog/hackerrank-remove-duplicates)
*   [[Easy] Rotate String (20 pts)](http://pidanic.com/blog/hackerrank-rotate-string)
*   [[Easy] Jumping Bunnies (20 pts)](http://pidanic.com/blog/hackerrank-jumping-bunnies/)
*   [[Easy] Missing Numbers (FP) (30 pts)](http://pidanic.com/en/blog/hackerrank-missing-numbers-fp/)

## Regex

#### Introduction

*   [[Easy] Matching Specific String (5 pts)](http://pidanic.com/blog/hackerrank-matching-specific-string)
*   [[Easy] Matching Word & Non-Word Character (5 pts)](http://pidanic.com/blog/hackerrank-matching-word-non-word-character)
*   [[Easy] Matching Digits & Non-Digit Characters (5 pts)](http://pidanic.com/blog/hackerrank-matching-digits-non-digit-characters)
*   [[Easy] Matching Whitespace & Non-Whitespace Character (5 pts)](http://pidanic.com/blog/hackerrank-matching-whitespace-non-whitespace-character)
*   [[Easy] Matching Anything But a Newline (5 pts)](http://pidanic.com/blog/hackerrank-matching-anything-newline/)
*   [[Easy] Matching Start & End (5 pts)](http://pidanic.com/blog/hackerrank-matching-start-end)

#### Character Class

*   [[Easy] Matching Specific Characters (10 pts)](http://pidanic.com/blog/hackerrank-matching-specific-characters)
*   [[Easy] Excluding Specific Characters (10 pts)](http://pidanic.com/blog/hackerrank-excluding-specific-characters)
*   [[Easy] Matching Range Of Characters (10 pts)](http://pidanic.com/blog/hackerrank-matching-range-characters/)

#### Repetitions

*   [[Easy] Matching {x} Repetitions (20 pts)](http://pidanic.com/blog/hackerrank-matching-x-repetitions)
*   [[Easy] Matching {x,y} Repetitions (20 pts)](http://pidanic.com/blog/hackerrank-matching-xy-repetitions)
*   [[Easy] Matching Zero Or More Repetitions (20 pts)](http://pidanic.com/blog/hackerrank-matching-zero-repetitions)
*   [[Easy] Matching One Or More Repetitions (20 pts)](http://pidanic.com/blog/hackerrank-matching-one-repetitions)
*   [[Easy] Matching Ending Items (20 pts)](http://pidanic.com/blog/hackerrank-matching-ending-items)

#### Grouping and Capturing

*   [[Easy] Matching Word Boundaries (20 pts)](http://pidanic.com/blog/hackerrank-matching-word-boundaries)
*   [[Easy] Capturing & Non-Capturing Groups (20 pts)](http://pidanic.com/blog/hackerrank-capturing-non-capturing-groups)
*   [[Easy] Alternative Matching (20 pts)](http://pidanic.com/blog/hackerrank-alternative-matching)

#### Applications

*   [[Easy] HackerRank Tweets (5 pts)](http://pidanic.com/blog/hackerrank-hackerrank-tweets)
*   [[Easy] Split the Phone Numbers (5 pts)](http://pidanic.com/blog/hackerrank-split-the-phone-numbers)
*   [[Easy] Find Hackerrank (5 pts)](http://pidanic.com/blog/hackerrank-find-hackerrank)
*   [[Easy] The British and American Style of Spelling (5 pts)](http://pidanic.com/blog/hackerrank-the-british-and-american-style-of-spelling)
*   [[Easy] Find a Substring (5 pts)](http://pidanic.com/blog/hackerrank-find-a-substring)
*   [[Easy] Alien Username (5 pts)](http://pidanic.com/blog/hackerrank-alien-username)
*   [[Easy] Detecting Valid Latitude and Longitude Pairs (20 pts)](http://pidanic.com/blog/hackerrank-detecting-valid-latitude-and-longitude-pairs)
*   [[Easy] Valid PAN Format (5 pts)](http://pidanic.com/blog/hackerrank-valid-pan-format)
*   [[Easy] IP Address Validation (10 pts)](http://pidanic.com/blog/hackerrank-ip-address-validation)
*   [[Easy] Detect HTML Attributes (10 pts)](http://pidanic.com/blog/hackerrank-detect-html-attributes)
*   [[Easy] Detect HTML Tags (10 pts)](http://pidanic.com/blog/hackerrank-detect-html-tags)

hackerrank

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