Solutions to Hackerrank practice problems

This repository contains 198 solutions to Hackerrank practice problems with Python 3.

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• Algorithms
  1. Warmup
     • Solve Me First | Problem | Solution | Difficulty: Easy | Score: 1
     • Simple Array Sum | Problem | Solution | Difficulty: Easy | Score: 10
     • Compare the Triplets | Problem | Solution | Difficulty: Easy | Score: 10
     • A Very Big Sum | Problem | Solution | Difficulty: Easy | Score: 10
     • Diagonal Difference | Problem | Solution | Difficulty: Easy | Score: 10
     • Plus Minus | Problem | Solution | Difficulty: Easy | Score: 10
     • Staircase | Problem | Solution | Difficulty: Easy | Score: 10
     • Mini-Max Sum | Problem | Solution | Difficulty: Easy | Score: 10
     • Birthday Cake Candles | Problem | Solution | Difficulty: Easy | Score: 10
     • Time Conversion | Problem | Solution | Difficulty: Easy | Score: 15
  2. Implementation
     • Sock Merchant | Problem | Solution | Difficulty: Easy | Score: 10
     • Counting Valleys | Problem | Solution | Difficulty: Easy | Score: 15
     • Jumping on the Clouds | Problem | Solution | Difficulty: Easy | Score: 20
     • Repeated String | Problem | Solution | Difficulty: Easy | Score: 20
     • Count Triplets | Problem | Solution | Difficulty: Medium | Score: 35
     • Frequency Queries | Problem | Solution | Difficulty: Medium | Score: 40
     • Grading Students | Problem | Solution | Difficulty: Easy | Score: 10
     • Apple and Orange | Problem | Solution | Difficulty: Easy | Score: 10
     • Kangaroo | Problem | Solution | Difficulty: Easy | Score: 10
     • Between Two Sets | Problem | Solution | Difficulty: Easy | Score: 10
     • Breaking The Records | Problem | Solution | Difficulty: Easy | Score: 10
     • Birthday Chocolate | Problem | Solution | Difficulty: Easy | Score: 10
     • Divisible Sum Pairs | Problem | Solution | Difficulty: Easy | Score: 10
     • Migratory Birds | Problem | Solution | Difficulty: Easy | Score: 10
     • Day of the Programmer | Problem | Solution | Difficulty: Easy | Score: 15
     • Bon Appetit | Problem | Solution | Difficulty: Easy | Score: 10
     • Drawing Book | Problem | Solution | Difficulty: Easy | Score: 10
     • Electronics Shop | Problem | Solution | Difficulty: Easy | Score: 15
     • Cats and a Mouse | Problem | Solution | Difficulty: Easy | Score: 15
     • Forming a Magic Square | Problem | Solution | Difficulty: Medium | Score: 20
     • Picking Numbers | Problem | Solution | Difficulty: Easy | Score: 20
     • Climbing the Leaderboard | Problem | Solution | Difficulty: Medium | Score: 20
     • The Hurdle Race | Problem | Solution | Difficulty: Easy | Score: 15
     • Designer PDF Viewer | Problem | Solution | Difficulty: Easy | Score: 20
     • Utopian Tree | Problem | Solution | Difficulty: Easy | Score: 20
     • Angry Professor | Problem | Solution | Difficulty: Easy | Score: 20
     • Beautiful Days at the Movies | Problem | Solution | Difficulty: Easy | Score: 15
     • Viral Advertising | Problem | Solution | Difficulty: Easy | Score: 15
     • Save the Prisoner! | Problem | Solution | Difficulty: Easy | Score: 15
     • Circular Array Rotation | Problem | Solution | Difficulty: Easy | Score: :20
     • Sequence Equation | Problem | Solution | Difficulty: Easy | Score: 20
     • Jumping on the Clouds; Revisited | Problem | Solution | Difficulty: Easy | Score: 15
     • Find Digits | Problem | Solution | Difficulty: Easy | Score: 25
     • Extra Long Factorials | Problem | Solution | Difficulty: Medium | Score: 20
     • Append and Delete | Problem | Solution | Difficulty: Easy | Score: 20
     • Sherlock and Squares | Problem | Solution | Difficulty: Easy | Score: 20
     • Library Fine | Problem | Solution | Difficulty: Easy | Score: 15
     • Cut the Sticks | Problem | Solution | Difficulty: Easy | Score: 25
     • Non-divisible Subset | Problem | Solution | Difficulty: Medium | Score: 20
     • Equalize the Array | Problem | Solution | Difficulty: Easy | Score: 20
     • Queen's Attack II | Problem | Solution | Difficulty: Medium | Score: 30
     • ACM ICPC Team | Problem | Solution | Difficulty: Easy | Score: 25
     • Taum and B'day | Problem | Solution | Difficulty: Easy | Score: 25
     • Organizing Containers of Balls | Problem | Solution | Difficulty: Medium | Score: 30
     • Encryption | Problem | Solution | Difficulty: Medium | Score: 30
     • Bigger is Greater | Problem | Solution | Difficulty: Medium | Score: 35
     • Modified Kaprekar Numbers | Problem | Solution | Difficulty: Easy | Score: 30
     • Beautiful Triplets | Problem | Solution | Difficulty: Easy | Score: 20
     • Minimum Distances | Problem | Solution | Difficulty: Easy | Score: 20
     • Halloween Sale | Problem | Solution | Difficulty: Easy | Score: 20
     • The Time in Words | Problem | Solution | Difficulty: Medium | Score: 25
     • Chocolate Feast | Problem | Solution | Difficulty: Easy | Score: 25
     • Service Lane | Problem | Solution | Difficulty: Easy | Score: 20
     • Lisa's Workbook | Problem | Solution | Difficulty: Easy | Score: 25
     • Flatland Space Stations | Problem | Solution | Difficulty: Easy | Score: 25
     • Fair Rations | Problem | Solution | Difficulty: Easy | Score: 25
     • Cavity Map | Problem | Solution | Difficulty: Easy | Score: 30
     • Manasa and Stones | Problem | Solution | Difficulty: Easy | Score: 30
     • The Grid Search | Problem | Solution | Difficulty: Medium | Score: 30
     • Happy Ladybugs | Problem | Solution | Difficulty: Easy | Score: 30
     • Strange Counter | Problem | Solution | Difficulty: Easy | Score: 30
     • 3D Surface Area | Problem | Solution | Difficulty: Medium | Score: 30
     • Absolute Permutation | Problem | Solution | Difficulty: Medium | Score: 40
     • The Bomberman Game | Problem | Solution | Difficulty: Medium | Score: 40
     • Ema's Supercomputer | Problem | Solution | Difficulty: Medium | Score: 40
     • arry's Array | Problem | Solution | Difficulty: Medium | Score: 40
     • Almost Sorted | Problem | Solution | Difficulty: Medium | Score: 50
     • Matrix Layer Rotation | Problem | Solution | Difficulty: Hard | Score: 80
  3. Strings
     • Hash Tables; Ransom Note | Problem | Solution | Difficulty: Easy | Score: 25
     • Two Strings | Problem | Solution | Difficulty: Easy | Score: 25
     • Sherlock and Anagrams | Problem | Solution | Difficulty: Medium | Score: 50
     • Making Anagrams | Problem | Solution | Difficulty: Easy | Score: 25
     • Alternating Characters | Problem | Solution | Difficulty: Easy | Score: 20
     • Sherlock and the Valid String | Problem | Solution | Difficulty: Medium | Score: 35
     • Special String Again | Problem | Solution | Difficulty: Medium | Score: 40
     • Common Child | Problem | Solution | Difficulty: Medium | Score: 60
     • Super Reduced String | Problem | Solution | Difficulty: Easy | Score: 10
     • CamelCase | Problem | Solution | Difficulty: Easy | Score: 15
     • Strong Password | Problem | Solution | Difficulty: Easy | Score: 15
     • Two Characters | Problem | Solution | Difficulty: Easy | Score: 20
     • Caesar Cipher | Problem | Solution | Difficulty: Easy | Score: 15
     • Mars Exploration | Problem | Solution | Difficulty: Easy | Score: 15
     • HackerRank in a String! | Problem | Solution | Difficulty: Easy | Score: 20
     • Pangrams | Problem | Solution | Difficulty: Easy | Score: 20
     • Weighted Uniform Strings | Problem | Solution | Difficulty: Easy | Score: 20
     • Separate the Numbers | Problem | Solution | Difficulty: Easy | Score: 20
     • Funny String | Problem | Solution | Difficulty: Easy | Score: 25
     • Gemstones | Problem | Solution | Difficulty: Easy | Score: 20
     • Beautiful Binary String | Problem | Solution | Difficulty: Easy | Score: 20
     • Making Anagrams | Problem | Solution | Difficulty: Easy | Score: 30
     • The Love-Letter Mystery | Problem | Solution | Difficulty: Easy | Score: 20
     • Palindrome Index | Problem | Solution | Difficulty: Easy | Score: 25
     • Determining DNA Health | Problem | Solution | Difficulty: Hard | Score: 50
     • Anagram | Problem | Solution | Difficulty: Easy | Score: 25
  4. Sorting
     • Bubble Sort | Problem | Solution | Difficulty: Easy | Score: 30
     • Comparator | Problem | Solution | Difficulty: Medium | Score: 35
     • Fraudulent Activity Notifications | Problem | Solution | Difficulty: Medium | Score: 40
     • Merge Sort; Counting Inversions | Problem | Solution | Difficulty: Hard | Score: 45
     • Big Sorting | Problem | Solution | Difficulty: Easy | Score: 20
     • Intro to Tutorial Challenges | Problem | Solution | Difficulty: Easy | Score: 30
     • Insertion Sort - Part 1 | Problem | Solution | Difficulty: Easy | Score: 30
     • Insertion Sort - Part 2 | Problem | Solution | Difficulty: Easy | Score: 30
     • Correctness and the Loop Invariant | Problem | Solution | Difficulty: Easy | Score: 30
     • Running Time of Algorithms | Problem | Solution | Difficulty: Easy | Score: 30
     • Quicksort 1 - Partition | Problem | Solution | Difficulty: Easy | Score: 10
     • Counting Sort 1 | Problem | Solution | Difficulty: Easy | Score: 30
     • Counting Sort 2 | Problem | Solution | Difficulty: Easy | Score: 30
     • The Full Counting Sort | Problem | Solution | Difficulty: Medium | Score: 40
     • Closest Numbers | Problem | Solution | Difficulty: Easy | Score: 35
     • Insertion Sort Advanced Analysis | Problem | Solution | Difficulty: Advanced | Score: 50
  5. Search
     • Hash Tables; Ice Cream Parlor | Problem | Solution | Difficulty: Medium | Score: 35
     • Pairs | Problem | Solution | Difficulty: Medium | Score: 50
     • Triple Sum | Problem | Solution | Difficulty: Medium | Score: 40
     • Minimum Time Required | Problem | Solution | Difficulty: Medium | Score: 35
     • Maximum Subarray Sum | Problem | Solution | Difficulty: Hard | Score: 65
     • Making Candies | Problem | Solution | Difficulty: Hard | Score: 45
  6. Greedy
     • Mark and Toys | Problem | Solution | Difficulty: Easy | Score: 35
     • Minimum Absolute Difference in an Array | Problem | Solution | Difficulty: Easy | Score: 15
     • Luck Balance | Problem | Solution | Difficulty: Easy | Score: 20
     • Greedy Florist | Problem | Solution | Difficulty: Medium | Score: 35
     • Max Min | Problem | Solution | Difficulty: Medium | Score: 35
     • Reverse Shuffle Merge | Problem | Solution | Difficulty: Advanced | Score: 50
  7. Constructive Algorithms
     • New Year Chaos | Problem | Solution | Difficulty: Medium | Score: 40
  8. Recursion
     • Recursive Digit Sum | Problem | Solution | Difficulty: Medium | Score: 30
• Data Structures
  1. Arrays
     • 2D Array - DS | Problem | Solution | Difficulty: Easy | Score: 15
     • Left Rotation | Problem | Solution | Difficulty: Easy | Score: 20
     • Minimum Swaps 2 | Problem | Solution | Difficulty: Medium | Score: 40
     • Array Manipulation | Problem | Solution | Difficulty: Hard | Score: 60
     • Arrays - DS | Problem | Solution | Difficulty: Easy | Score: 10
     • Dynamic Array | Problem | Solution | Difficulty: Easy | Score: 15
     • Sparse Arrays | Problem | Solution | Difficulty: Medium | Score: 25
  2. Linked Lists
     • Print the Elements of a Linked List | Problem | Solution | Difficulty: Easy | Score: 5
     • Insert a Node at the Tail of Linked List | Problem | Solution | Difficulty: Easy | Score: 5
     • Insert a node at the head of a linked list | Problem | Solution | Difficulty: Easy | Score: 5
     • Insert a node at a specific position in a linked list | Problem | Solution | Difficulty: Easy | Score: 5
     • Delete a Node | Problem | Solution | Difficulty: Easy | Score: 5
     • Print in Reverse | Problem | Solution | Difficulty: Easy | Score: 5
     • Reverse a linked list | Problem | Solution | Difficulty: Easy | Score: 5
  3. Trees
     • Swap Nodes [Algo] | Problem | Solution | Difficulty: Medium | Score: 40
• Tutorial
  1. 10 Days of Statistics
     • Day 0; Mean, Median, and Mode | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 0; Weighted Mean | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 1; Quartiles | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 1; Interquartile Range | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 1; Standard Deviation | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 4; Binomial Distribution I | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 4; Binomial Distribution II | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 4; Geometric Distribution I | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 4; Geometric Distribution II | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 5; Poisson Distribution I | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 5; Poisson Distribution II | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 5; Normal Distribution I | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 5; Normal Distribution II | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 6; The Central Limit Theorem I | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 6; The Central Limit Theorem II | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 6; The Central Limit Theorem III | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 7; Pearson Correlation Coefficient I | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 7; Spearman's Rank Correlation Coefficient | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 8; Least Square Regression Line | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 9; Multiple Linear Regression | Problem | Solution | Difficulty: Medium | Score: 30
  2. 30 Days of Code
     • Day 0; Hello, World | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 1; Data Types | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 2; Operators | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 3; Intro to Conditional Statements | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 4; Class vs Instance | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 5; Loops | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 6; Let's Review | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 7; Arrays | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 8; Dictionaries and Maps | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 9; Recursion 3 | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 10; Binary Numbers | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 11; 2D Arrays | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 12; Inheritance | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 13; Abastact Classes | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 14; Scope | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 15; Linked List | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 16; Exceptions - String to Integer | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 17; More Exceptions | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 18; Queue and Stacks | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 19; Interfaces | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 20; Sorting | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 22; Binary Search Trees | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 23; BST Level-Order Traversal | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 24; More Linked Lists | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 25; Running Time and Complexity | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 26; Nested Logic | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 27; Testing | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 28; RegEx, Patterns, and Intro to Databases | Problem | Solution | Difficulty: Easy | Score: 30
     • Day 29; Bitwise AND | Problem | Solution | Difficulty: Easy | Score: 30