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Solutions to problems on HackerRank

• Java
• Python
• SQL
• Cracking the Coding Interview
• Interview Preparation Kit
• Functional Programming

Java

| Subdomain | Challenge | Score | Difficulty | Solution | |:---------------------------:|:------------------------------------------------------------------------------------------------------------------------:|:------:|:----------:|:----------------------------------------------------------------------------------------------------------------------:| | Introduction | Welcome to Java! | 3 | Easy | Solution.java | | Introduction | Java Stdin and Stdout I | 5 | Easy | Solution.java | | Introduction | Java If-Else | 10 | Easy | Solution.java | | Introduction | Java Stdin and Stdout II | 10 | Easy | Solution.java | | Introduction | Java Output Formatting | 10 | Easy | Solution.java | | Introduction | Java Loops I | 10 | Easy | Solution.java | | Introduction | Java Loops II | 10 | Easy | Solution.java | | Introduction | Java Datatypes | 10 | Easy | Solution.java | | Introduction | Java End-of-file | 10 | Easy | Solution.java | | Introduction | Java Static Initializer Block | 10 | Easy | Solution.java | | Introduction | Java Int to String | 10 | Easy | Solution.java | | Introduction | Java Date and Time | 15 | Easy | Solution.java | | Introduction | Java Currency Formatter | 15 | Easy | Solution.java | | Strings | Java Strings Introduction | 5 | Easy | Solution.java | | Strings | Java Substring | 5 | Easy | Solution.java | | Strings | Java Substring Comparisons | 10 | Easy | Solution.java | | Strings | Java String Reverse | 10 | Easy | Solution.java | | Strings | Java Anagrams | 10 | Easy | Solution.java | | Strings | Java String Tokens | 15 | Easy | Solution.java | | Strings | Pattern Syntax Checker | 20 | Easy | Solution.java | | Strings | Java Regex | 25 | Medium | Solution.java | | Strings | Java Regex 2 - Duplicate Words | 25 | Medium | Solution.java | | Strings | Valid Username Regular Expression | 20 | Easy | Solution.java | | Strings | Tag Content Extractor | 20 | Medium | Solution.java | | BigNumber | Java BigInteger | 10 | Easy | Solution.java | | BigNumber | Java BigDecimal | 20 | Medium | Solution.java | | BigNumber | Java Primality Test | 20 | Easy | Solution.java | | Data Structures | Java 1D Array | 5 | Easy | Solution.java | | Data Structures | Java 2D Array | 10 | Easy | Solution.java | | Data Structures | Java Subarray | 10 | Easy | Solution.java | | Data Structures | Java Arraylist | 10 | Easy | Solution.java | | Data Structures | Java 1D Array (Part 2) | 25 | Medium | Solution.java | | Data Structures | Java List | 15 | Easy | Solution.java | | Data Structures | Java Map | 10 | Easy | Solution.java | | Data Structures | Java Stack | 20 | Medium | Solution.java | | Data Structures | Java Hashset | 10 | Easy | Solution.java | | Data Structures | Java Generics | 15 | Easy | Solution.java | | Data Structures | Java Comparator | 10 | Medium | Solution.java | | Data Structures | Java Sort | 10 | Easy | Solution.java | | Data Structures | Java Dequeue | 20 | Medium | Solution.java | | Data Structures | Java BitSet | 20 | Easy | Solution.java | | Data Structures | Java Priority Queue | 20 | Medium | Solution.java | | Object Oriented Programming | Java Inheritance I | 5 | Easy | Solution.java | | Object Oriented Programming | Java Inheritance II | 10 | Easy | Solution.java | | Object Oriented Programming | Java Abstract Class | 10 | Easy | Solution.java | | Object Oriented Programming | Java Interface | 10 | Easy | Solution.java | | Object Oriented Programming | Java Method Overriding | 10 | Easy | Solution.java | | Object Oriented Programming | Java Method Overriding 2 (Super Keyword) | 10 | Easy | Solution.java | | Object Oriented Programming | Java Instanceof keyword | 10 | Easy | Solution.java | | Object Oriented Programming | Java Iterator | 15 | Easy | Solution.java | | Exception Handling | Java Exception Handling (Try-catch) | 10 | Easy | Solution.java | | Exception Handling | Java Exception Handling | 15 | Easy | Solution.java | | Advanced | Java Varargs - Simple Addition | 15 | Easy | Solution.java | | Advanced | Java Reflection - Attributes | 15 | Easy | Solution.java | | Advanced | Can You Access | 15 | Medium | Solution.java | | Advanced | Prime Checker | 25 | Medium | Solution.java | | Advanced | Java Factory Pattern | 15 | Easy | Solution.java | | Advanced | Java Singleton Pattern | 15 | Easy | Solution.java | | Advanced | Java Visitor Pattern | 40 | Medium | Solution.java | | Advanced | Java Annotations | 25 | Medium | Solution.java | | Advanced | Covariant Return Types | 20 | Easy | Solution.java | | Advanced | Java Lambda Expressions | 30 | Medium | Solution.java | | Advanced | Java MD5 | 30 | Medium | Solution.java | | Advanced | Java SHA-256 | 30 | Medium | Solution.java |

Python

| Subdomain | Challenge | Score | Difficulty | Solution | |:---------------------------:|:-------------------------------------------------------------------------------------------------------------------------------------------:|:------:|:----------:|:----------------------------------------------------------------------------------------------------------------------:| | Introduction | Say "Hello, World!" With Python | 5 | Easy | Solution.py | | Introduction | Python If-Else | 10 | Easy | Solution.py | | Introduction | Arithmetic Operators | 10 | Easy | Solution.py | | Introduction | Python: Division | 10 | Easy | Solution.py | | Introduction | Loops | 10 | Easy | Solution.py | | Introduction | Write a function | 10 | Medium | Solution.py | | Introduction | Print Function | 20 | Easy | Solution.py | | Basic Data Types | List Comprehensions | 10 | Easy | Solution.py | | Basic Data Types | Find the Runner-Up Score! | 10 | Easy | Solution.py | | Basic Data Types | Nested Lists | 10 | Easy | Solution.py | | Basic Data Types | Finding the percentage | 10 | Easy | Solution.py | | Basic Data Types | Lists | 10 | Easy | Solution.py | | Basic Data Types | Tuples | 10 | Easy | Solution.py | | Strings | sWAP cASE | 10 | Easy | Solution.py | | Strings | String Split and Join | 10 | Easy | Solution.py | | Strings | What's Your Name? | 10 | Easy | Solution.py | | Strings | Mutations | 10 | Easy | Solution.py | | Strings | Find a string | 10 | Easy | Solution.py | | Strings | String Validators | 10 | Easy | Solution.py | | Strings | Text Alignment | 10 | Easy | Solution.py | | Strings | Text Wrap | 10 | Easy | Solution.py | | Strings | Designer Door Mat | 10 | Easy | Solution.py | | Strings | String Formatting | 10 | Easy | Solution.py | | Strings | Alphabet Rangoli | 20 | Easy | Solution.py | | Strings | Capitalize! | 20 | Easy | Solution.py | | Strings | The Minion Game | 40 | Medium | Solution.py | | Strings | Merge the Tools! | 40 | Medium | Solution.py | | Sets | Introduction to Sets | 10 | Easy | Solution.py | | Sets | No Idea! | 50 | Medium | Solution.py | | Sets | Symmetric Difference | 10 | Easy | Solution.py | | Sets | Set .add() | 10 | Easy | Solution.py | | Sets | Set .discard(), .remove() & .pop() | 10 | Easy | Solution.py | | Sets | Set .union() Operation | 10 | Easy | Solution.py | | Sets | Set .intersection() Operation | 10 | Easy | Solution.py | | Sets | Set .difference() Operation | 10 | Easy | Solution.py | | Sets | Set .symmetric_difference() Operation | 10 | Easy | Solution.py | | Sets | Set Mutations | 10 | Easy | Solution.py | | Sets | The Captain's Room | 10 | Easy | Solution.py | | Sets | Check Subset | 10 | Easy | Solution.py | | Sets | Check Strict Superset | 10 | Easy | Solution.py | | Math | Polar Coordinates | 10 | Easy | Solution.py | | Math | Find Angle MBC | 10 | Medium | Solution.py | | Math | Triangle Quest 2 | 20 | Medium | Solution.py | | Math | Mod Divmod | 10 | Easy | Solution.py | | Math | Power - Mod Power | 10 | Easy | Solution.py | | Math | Integers Come In All Sizes | 10 | Easy | Solution.py | | Math | Triangle Quest | 20 | Medium | Solution.py | | Itertools | itertools.product() | 10 | Easy | Solution.py | | Itertools | itertools.permutations() | 10 | Easy | Solution.py | | Itertools | itertools.combinations() | 10 | Easy | Solution.py | | Itertools | itertools.combinationswithreplacement() | 10 | Easy | Solution.py | | Itertools | Compress the String! | 20 | Medium | Solution.py | | Itertools | Iterables and Iterators | 40 | Medium | Solution.py | | Itertools | Maximize It! | 50 | Hard | Solution.py | | Collections | Collections.Counter() | 10 | Easy | Solution.py | | Collections | DefaultDict Tutorial | 20 | Easy | Solution.py | | Collections | Collections.namedtuple() | 20 | Easy | Solution.py | | Collections | Collections.OrderedDict() | 20 | Easy | Solution.py | | Collections | Word Order | 50 | Medium | Solution.py | | Collections | Collections.deque() | 20 | Easy | Solution.py | | Collections | Company Logo | 30 | Medium | Solution.py | | Collections | Piling Up! | 50 | Medium | Solution.py | | Date and Time | Calendar Module | 10 | Easy | Solution.py | | Date and Time | Time Delta | 30 | Medium | Solution.py | | Errors and Exceptions | Exceptions | 10 | Easy | Solution.py | | Errors and Exceptions | Incorrect Regex | 20 | Easy | Solution.py | | Classes | Classes: Dealing with Complex Numbers | 20 | Medium | Solution.py | | Classes | Class 2 - Find the Torsional Angle | 20 | Easy | Solution.py | | Built-Ins | Zipped! | 10 | Easy | Solution.py | | Built-Ins | Input() | 20 | Easy | Solution.py | | Built-Ins | Python Evaluation | 20 | Easy | Solution.py | | Built-Ins | Athlete Sort | 30 | Medium | Solution.py | | Built-Ins | Any or All | 20 | Easy | Solution.py | | Built-Ins | ginortS | 40 | Medium | Solution.py | | Python Functionals | Map and Lambda Function | 20 | Easy | Solution.py | | Python Functionals | Validating Email Addresses With a Filter | 20 | Medium | Solution.py | | Python Functionals | Reduce Function | 30 | Medium | Solution.py | | Regex and Parsing | Detect Floating Point Number | 20 | Easy | Solution.py | | Regex and Parsing | Re.split() | 20 | Easy | Solution.py | | Regex and Parsing | Group(), Groups() & Groupdict() | 20 | Easy | Solution.py | | Regex and Parsing | Re.findall() & Re.finditer() | 20 | Easy | Solution.py | | Regex and Parsing | Re.start() & Re.end() | 20 | Easy | Solution.py | | Regex and Parsing | Regex Substitution | 20 | Medium | Solution.py | | Regex and Parsing | Validating Roman Numerals | 20 | Easy | Solution.py | | Regex and Parsing | Validating phone numbers | 20 | Easy | Solution.py | | Regex and Parsing | Validating and Parsing Email Addresses | 20 | Easy | Solution.py | | Regex and Parsing | Hex Color Code | 30 | Easy | Solution.py | | Regex and Parsing | HTML Parser - Part 1 | 30 | Easy | Solution.py | | Regex and Parsing | HTML Parser - Part 2 | 30 | Easy | Solution.py | | Regex and Parsing | Detect HTML Tags, Attributes and Attribute Values | 30 | Easy | Solution.py | | Regex and Parsing | Validating UID | 40 | Easy | Solution.py | | Regex and Parsing | Validating Credit Card Numbers | 40 | Medium | Solution.py | | Regex and Parsing | Validating Postal Codes | 80 | Hard | Solution.py | | Regex and Parsing | Matrix Script | 100 | Hard | Solution.py | | XML | XML 1 - Find the Score | 20 | Easy | Solution.py | | XML | XML2 - Find the Maximum Depth | 20 | Easy | Solution.py | | Closures and Decorators | Standardize Mobile Number Using Decorators | 30 | Easy | Solution.py | | Closures and Decorators | Decorators 2 - Name Directory | 30 | Easy | Solution.py | | Numpy | Arrays | 20 | Easy | Solution.py | | Numpy | Shape and Reshape | 20 | Easy | Solution.py | | Numpy | Transpose and Flatten | 20 | Easy | Solution.py | | Numpy | Concatenate | 20 | Easy | Solution.py | | Numpy | Zeros and Ones | 20 | Easy | Solution.py | | Numpy | Eye and Identity | 20 | Easy | Solution.py | | Numpy | Array Mathematics | 20 | Easy | Solution.py | | Numpy | Floor, Ceil and Rint | 20 | Easy | Solution.py | | Numpy | Sum and Prod | 20 | Easy | Solution.py | | Numpy | Min and Max | 20 | Easy | Solution.py | | Numpy | Mean, Var, and Std | 20 | Easy | Solution.py | | Numpy | Dot and Cross | 20 | Easy | Solution.py | | Numpy | Inner and Outer | 20 | Easy | Solution.py | | Numpy | Polynomials | 20 | Easy | Solution.py | | Numpy | Linear Algebra | 20 | Easy | Solution.py | | Debugging | Words Score | 10 | Medium | Solution.py | | Debugging | Default Arguments | 30 | Medium | Solution.py |

SQL

| Subdomain | Challenge | Score | Difficulty | Solution | |:---------------------------:|:----------------------------------------------------------------------------------------------------------------------------:|:------:|:----------:|:-------------------------------------------------------------------------------------------------:| | Basic Select | Revising the Select Query I | 10 | Easy | Solution.sql | | Basic Select | Revising the Select Query II | 10 | Easy | Solution.sql | | Basic Select | Select All | 10 | Easy | Solution.sql | | Basic Select | Select By ID | 10 | Easy | Solution.sql | | Basic Select | Japanese Cities' Attributes | 10 | Easy | Solution.sql | | Basic Select | Japanese Cities' Names | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 1 | 15 | Easy | Solution.sql | | Basic Select | Weather Observation Station 3 | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 4 | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 5 | 30 | Easy | Solution.sql | | Basic Select | Weather Observation Station 6 | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 7 | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 8 | 15 | Easy | Solution.sql | | Basic Select | Weather Observation Station 9 | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 10 | 10 | Easy | Solution.sql | | Basic Select | Weather Observation Station 11 | 15 | Easy | Solution.sql | | Basic Select | Weather Observation Station 12 | 15 | Easy | Solution.sql | | Basic Select | Higher Than 75 Marks | 15 | Easy | Solution.sql | | Basic Select | Employee Names | 10 | Easy | Solution.sql | | Basic Select | Employee Salaries | 10 | Easy | Solution.sql | | Advanced Select | The PADS | 30 | Medium | Solution.sql | | Advanced Select | Type of Triangle | 20 | Easy | Solution.sql | | Advanced Select | Occupations | 30 | Medium | Solution.sql | | Advanced Select | Binary Tree Nodes | 30 | Medium | Solution.sql | | Advanced Select | New Companies | 30 | Medium | Solution.sql | | Aggregation | Revising Aggregations - The Count Function | 10 | Easy | Solution.sql | | Aggregation | Revising Aggregations - The Sum Function | 10 | Easy | Solution.sql | | Aggregation | Revising Aggregations - Averages | 10 | Easy | Solution.sql | | Aggregation | Average Population | 10 | Easy | Solution.sql | | Aggregation | Japan Population | 10 | Easy | Solution.sql | | Aggregation | Population Density Difference | 10 | Easy | Solution.sql | | Aggregation | The Blunder | 15 | Easy | Solution.sql | | Aggregation | Top Earners | 20 | Easy | Solution.sql | | Aggregation | Weather Observation Station 2 | 15 | Easy | Solution.sql | | Aggregation | Weather Observation Station 13 | 10 | Easy | Solution.sql | | Aggregation | Weather Observation Station 14 | 10 | Easy | Solution.sql | | Aggregation | Weather Observation Station 15 | 15 | Easy | Solution.sql | | Aggregation | Weather Observation Station 16 | 10 | Easy | Solution.sql | | Aggregation | Weather Observation Station 17 | 15 | Easy | Solution.sql | | Aggregation | Weather Observation Station 18 | 25 | Medium | Solution.sql | | Aggregation | Weather Observation Station 19 | 30 | Medium | Solution.sql | | Aggregation | Weather Observation Station 20 | 40 | Medium | Solution.sql | | Basic Join | Asian Population | 10 | Easy | Solution.sql | | Basic Join | African Cities | 10 | Easy | Solution.sql | | Basic Join | Average Population of Each Continent | 10 | Easy | Solution.sql | | Basic Join | The Report | 20 | Medium | Solution.sql | | Basic Join | Top Competitors | 30 | Medium | Solution.sql | | Basic Join | Ollivander's Inventory | 30 | Medium | Solution.sql | | Basic Join | Challenges | 30 | Medium | Solution.sql | | Basic Join | Contest Leaderboard | 30 | Medium | Solution.sql | | Advanced Join | Projects | 40 | Medium | Solution.sql | | Advanced Join | Placements | 40 | Medium | Solution.sql | | Advanced Join | Symmetric Pairs | 40 | Medium | Solution.sql | | Advanced Join | Interviews | 50 | Hard | Solution.sql | | Advanced Join | 15 Days of Learning SQL | 50 | Hard | Solution.sql | | Alternative Queries | Draw The Triangle 1 | 25 | Easy | Solution.sql | | Alternative Queries | Draw The Triangle 2 | 25 | Easy | Solution.sql | | Alternative Queries | Print Prime Numbers | 40 | Medium | Solution.sql |

Cracking the Coding Interview

| Subdomain | Challenge | Score | Difficulty | Solution | |:----------------------:|:--------------------------------------------------------------------------------------------------------:|:------:|:----------:|:-----------------------------------------------------------------------------------------------------------------------------------:| | Data Structures | Arrays: Left Rotation | 20 | Easy | Solution.java | | Data Structures | Strings: Making Anagrams | 25 | Easy | Solution.java | | Data Structures | Hash Tables: Ransom Note | 25 | Easy | Solution.java | | Data Structures | Linked Lists: Detect a Cycle | 25 | Easy | Solution.java | | Data Structures | Stacks: Balanced Brackets | 30 | Medium | Solution.java | | Data Structures | Queues: A Tale of Two Stacks | 30 | Medium | Solution.java | | Data Structures | Trees: Is This a Binary Search Tree? | 30 | Medium | Solution.java | | Data Structures | Heaps: Find the Running Median | 50 | Hard | Solution.java | | Data Structures | Tries: Contacts | 50 | Hard | Solution.java | | Algorithms | Sorting: Bubble Sort | 30 | Medium | Solution.java | | Algorithms | Sorting: Comparator | 35 | Medium | Solution.java | | Algorithms | Merge Sort: Counting Inversions | 45 | Hard | Solution.java | | Algorithms | Hash Tables: Ice Cream Parlor | 35 | Medium | Solution.java | | Algorithms | DFS: Connected Cell in a Grid | 45 | Hard | Solution.java | | Algorithms | BFS: Shortest Reach in a Graph | 45 | Hard | Solution.java | | Techniques / Concepts | Time Complexity: Primality | 30 | Medium | Solution.java | | Techniques / Concepts | Recrusion: Fibonacci Numbers | 15 | Easy | Solution.java | | Techniques / Concepts | Recursion: Davis' Staircase | 30 | Medium | Solution.java | | Techniques / Concepts | DP: Coin Change | 60 | Hard | Solution.java | | Techniques / Concepts | Bit Manipulation: Lonely Integer | 20 | Easy | Solution.java |

Interview Preparation Kit

| Subdomain | Challenge | Score | Difficulty | Solution | |:--------------------------:|:----------------------------------------------------------------------------------------------------------------------------:|:------:|:----------:|:----------------------------------------------------------------------------------------------------------------------------------:| | Warm-up Challenges | Sock Merchant | 10 | Easy | Solution.java | | Warm-up Challenges | Counting Valleys | 15 | Easy | Solution.java | | Warm-up Challenges | Jumping on the Clouds | 20 | Easy | Solution.java | | Warm-up Challenges | Repeated String | 20 | Easy | Solution.java | | Arrays | 2D Array - DS | 15 | Easy | Solution.java | | Arrays | Arrays: Left Rotation | 20 | Easy | Solution.java | | Arrays | New Year Chaos | 40 | Medium | Solution.java | | Arrays | Minimum Swaps 2 | 40 | Medium | Solution.java | | Arrays | Array Manipulation | 60 | Hard | Solution.java | | Dictionaries and Hashmaps | Hash Tables: Ransom Note | 25 | Easy | Solution.java | | Dictionaries and Hashmaps | Two Strings | 25 | Easy | Solution.java | | Dictionaries and Hashmaps | Sherlock and Anagrams | 50 | Medium | Solution.java | | Sorting | Sorting: Bubble Sort | 30 | Easy | Solution.java | | Sorting | Mark and Toys | 35 | Easy | Solution.java | | Sorting | Sorting: Comparator | 35 | Medium | Solution.java | | Sorting | Merge Sort: Counting Inversions | 45 | Hard | Solution.java | | String Manipulation | Strings: Making Anagrams | 25 | Easy | Solution.java | | String Manipulation | Alternating Characters | 20 | Easy | Solution.java | | Greedy Algorithms | Minimum Absolute Difference in an Array | 15 | Easy | Solution.java | | Greedy Algorithms | Luck Balance | 20 | Easy | Solution.java | | Greedy Algorithms | Greedy Florist | 35 | Medium | Solution.java | | Greedy Algorithms | Max Min | 35 | Medium | Solution.java | | Search | Hash Tables: Ice Cream Parlor | 35 | Medium | Solution.java | | Search | Pairs | 50 | Medium | Solution.java | | Dynamic Programming | Max Array Sum | 20 | Medium | Solution.java | | Dynamic Programming | Candies | 50 | Medium | Solution.java | | Stacks and Queues | Balanced Brackets | 25 | Medium | Solution.java | | Stacks and Queues | Queues: A Tale of Two Stacks | 30 | Medium | Solution.java | | Graphs | BFS: Shortest Reach in a Graph | 45 | Hard | Solution.java | | Graphs | DFS: Connected Cell in a Grid | 45 | Hard | Solution.java | | Trees | Tree: Height of a Binary Tree | 10 | Easy | Solution.java | | Trees | Trees: Is This a Binary Search Tree? | 30 | Medium | Solution.java | | Trees | Binary Search Tree: Lowest Common Ancestor| 30 | Easy | Solution.java | | Linked Lists | Linked Lists: Detect a Cycle | 25 | Easy | Solution.java | | Linked Lists | Reverse a Doubly Linked List | 5 | Easy | Solution.java | | Linked Lists | Find Merge Point of Two Lists | 5 | Easy | Solution.java | | Recursion and Backtracking | Recursion: Fibonacci Numbers | 15 | Easy | Solution.java | | Recursion and Backtracking | Recursion: Davis' Staircase | 30 | Medium | Solution.java | | Miscellaneous | Flipping bits | 40 | Easy | Solution.java | | Miscellaneous | Time Complexity: Primality | 30 | Medium | Solution.java |

Functional Programming

| Subdomain | Challenge | Score | Difficulty | Solution | |:----------------------:|:--------------------------------------------------------------------------------------------------------:|:------:|:----------:|:-----------------------------------------------------------------------------------------------------------------------------------:| | Introduction | Solve Me First FP | 3 | Easy | Solution.scala | | Introduction | Hello World | 5 | Easy | Solution.scala |