RyanFehr/HackerRank

Solutions to problems on HackerRank.

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Algorithms

• Warmup
• Implementation
• Strings
• Sorting
• Search
• Graph Theory
• Greedy
• Dynamic Programming
• Constructive Algorithms
• Bit Manipulation
• Recursion
• Game Theory
• NP Complete

DataStructures

• Arrays
• Linked Lists
• Trees
• Balanced Trees
• Stacks
• Queues
• Heap
• Disjoint Set
• Multiple Choice
• Trie
• Advanced

Mathematics

• Fundamentals
• Number Theory
• Combinatorics
• Algebra
• Geometry
• Probability
• Linear Algebra Foundations

Java

• Introduction
• Strings
• BigNumber
• Data Structures
• Object Oriented Programming
• Exception Handling
• Advanced

Warmup

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Solve Me First	Java C#	O(1)	O(1)	Easy	1
	Simple Array Sum	Java C#	O(n)	O(1)	Easy	10
	Compare the Triplets	Java C#	O(1)	O(1)	Easy	10
	A Very Big Sum	Java C#	O(n)	O(1)	Easy	10
	Diagonal Difference	Java C#	O(n)	O(1)	Easy	10
	Plus Minus	Java C#	O(n)	O(1)	Easy	10
	Staircase	Java C#	O(n)	O(n)	Easy	10
	Mini-Max Sum	Java C#	O(1)	O(1)	Easy	10
	Time Conversion	Java C#	O(1)	O(1)	Easy	15
	Birthday Cake Candles	Java C#	O(n)	O(1)	Easy	10

Implementation

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Grading Students	Java JS C#	O(n)	O(1)	Easy	10
	Apple and Orange	Java JS C#	O(n+m)	O(1)	Easy	10
	Kangaroo	Java C#	O(1)	O(1)	Easy	10
	Between Two Sets	Java C#	O(x(n+m))	O(1)	Easy	10	x=(max(m) - min(n))/min(n)
	Divisible Sum Pairs	Java C#	O(n^2)	O(1)	Easy	10
	Birthday Chocolate	Java C#	O(n)	O(1)	Easy	10
	Breaking the Records	Java C#	O(n)	O(1)	Easy	10
	Migratory Birds	Java JS C#	O(n)	O(1)	Easy	10
	Day of the Programmer	Java C#	O(1)	O(1)	Easy	15
	Bon Appetit	Java C#	O(n)	O(1)	Easy	10
	Sock Merchant	Java C#	O(n)	O(n)	Easy	10
	Drawing Book	Java C#	O(1)	O(1)	Easy	10
	Counting Valleys	Java JS C#	O(n)	O(1)	Easy	15
	Cats and a Mouse	Java C#	O(1)	O(1)	Easy	15
	Electronics Shop	Java JS C#	O(n log (n))	O(1)	Easy	15	n = m+n
	Picking Numbers	Java C#	O(n)	O(n)	Easy	20
	Climbing the Leaderboard	Java JS C#	O(n+m)	(n)	Easy	20
	The Hurdle Race	Java C#	O(n)	O(1)	Easy	15
	Designer PDF Viewer	Java JS C#	O(n)	O(n)	Easy	20
	Forming a Magic Square	Java	O(1)	O(1)	Easy	20
	Utopian Tree	Java JS C#	O(n)	O(1)	Easy	20
	Angry Professor	Java JS C#	O(n)	O(1)	Easy	20
	Beautiful Days at the Movies	Java JS C#	O(n)	O(1)	Easy	15
	Viral Advertising	Java JS C#	O(n)	O(1)	Easy	15
	Save the Prisoner!	Java C#	O(1)	O(1)	Easy	15
	Circular Array Rotation	Java C#	O(n)	O(1)	Easy	20
	Sequence Equation	Java C#	O(n)	O(n)	Easy	20
	Jumping on the Clouds: Revisited	Java C#	O(n)	O(n)	Easy	15
	Find Digits	Java C#	O(n)	O(1)	Easy	25
	Extra Long Factorials	Java C#	O(n)	O(1)	Medium	20
	Append and Delete	Java	O(n)	O(1)	Easy	20
	Sherlock and Squares	Java	O(n)	O(1)	Easy	20
	Library Fine	Java C#	O(1)	O(1)	Easy	15
	Cut the sticks	Java C#	O(n log(n))	O(n)	Easy	25
	Non-Divisible Subset	Java	O(n)	O(n)	Medium	20
	Repeated String	Java C#	O(n)	O(n)	Easy	20
	Jumping on the Clouds	Java C#	O(n)	O(n)	Easy	20
	Equalize the Array	Java C#	O(n)	O(n)	Easy	20
	Queen's Attack II	Java	O(k)	O(1)	Medium	30
	ACM ICPC Team	Java	O(n^3)	O(n)	Easy	25
	Taum and B'day	Java C#	O(1)	O(1)	Easy	25
	Organizing Containers of Balls	Java	O(n^2)	O(n^2)	Medium	30
	Encryption	Java C#	O(n)	O(1)	Medium	30
	Bigger is Greater	Java	O(n)	O(n)	Medium	35
	Modified Kaprekar Numbers	Java C#	O(n)	O(1)	Easy	30
	Minimum Distances	Java C#	O(n)	O(n)	Easy	20
	Beautiful Triplets	Java C#	O(n)	O(n)	Easy	20
	Strings: Making Anagrams	Java	O(|a|+|b|)	O(1)	Easy	30
	The Time in Words	Java C#	O(1)	O(1)	Medium	25
	Chocolate Feast	Java C#	O(log(n))	O(1)	Easy	25	Base of logarithmic time complexity is m
	Service Lane	Java C#	O(n)	O(n)	Easy	20
	Lisa's Workbook	Java C#	O(n)	O(1)	Easy	25
	Flatland Space Stations	Java C#	O(n)	O(n)	Easy	25
	Fair Rations	Java C#	O(n)	O(1)	Easy	25
	Cavity Map	Java C#	O(n^2)	O(n^2)	Easy	30
	Manasa and Stones	Java C#	O(n)	O(1)	Easy	30
	The Grid Search	Java	O(n)	O(n)	Medium	30	n = len(word)
	Happy Ladybugs	Java	O(n)	O(n)	Easy	30
	Strange Counter	Java	O(n)	O(1)	Easy	30	n = t
	Absolute Permuation	Java	O(n)	O(n)	Medium	40
	The Bomberman Game	Java	O(n*m)	O(n*m)	Medium	40
	Ema's Supercomputer	Java			Medium	40
	Larry's Array	Java			Medium	40
	Almost Sorted	Java			Medium	50
	Matrix Layer Rotation	Python3	O(n*m)	O(n*m)	Hard	80
	Consecutive 1s in Binary Numbers	Java	O(n)	O(1)	Easy	30
	Nested Logic	Java	O(1)	O(1)	Easy	40
	Bitwise AND	Java	O(1)	O(1)	Easy	20

Strings

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Super Reduced String	Java C#	O(n)	O(n)	Easy	10
	camelCase	Java C#	O(n)	O(1)	Easy	15
	Strong Password	C#	O(n)	O(1)	Easy	15
	Two Characters	Java C#	O(n)	O(n)	Easy	15
	Caesar Cipher	Java C#	O(n)	O(n)	Easy	15
	Caesar Cipher: Encryption	Java	O(n)	O(n)	Easy	40
	Mars Exploration	Java C#	O(n)	O(1)	Easy	15
	HackerRank in a String!	Java JS C#	O(n)	O(1)	Easy	20
	Pangrams	Java C#	O(n)	O(1)	Easy	20
	Weighted Uniform Strings	Java C#	O(n)	O(n)	Easy	20
	Separate the Numbers	Java C#	O(n)	O(n)	Easy	20
	Funny String	Java C#	O(n)	O(n)	Easy	25
	Gemstones	Java C#	O(n)	O(1)	Easy	20
	Alternating Characters	Java C#	O(n)	O(1)	Easy	20
	Beautiful Binary String	Java	O(n)	O(1)	Easy	20
	The Love-Letter Mystery	Java	O(n)	O(1)	Easy	20
	Determining DNA Health	Java			Hard	50
	Palindrome Index	Java	O(n)	O(1)	Easy	25
	Anagram	Java	O(n)	O(1)	Easy	25
	Making Anagrams	Java	O(n)	O(n)	Easy	30
	Game of Thrones - I	Java C#	O(n)	O(1)	Easy	30
	Two Strings	Java C#	O(|a| + |b|)	O(1)	Easy	25	a and b are lengths of the input strings
	String Construction	Java	O(n)	O(n)	Easy	25
	Sherlock and Valid String	Java	O(n)	O(n)	Hard	100
	Richie Rich	Java Python3	O(n)	O(n)	Medium	30
	Sherlock and Anagrams	Java			Medium	50
	Common Child	Java			Hard	60
	Bear and Steady Gene	Java			Medium	50
	Morgan and a String	Java	O((|a|+|b|)^2)	O(|a| + |b|)	Expert	100
	Count Strings	Java			Hard	80
	String Function Calculation	Java			Advanced	80
	Build a Palindrome	Java			Advanced	80
	Build a String	Java			Hard	80
	Gridland Provinces	Java			Hard	80
	Ashton and String	Java			Advanced	100
	String Similarity	Java			Expert	100
	Super Functional Strings	Java			Advanced	80
	Circular Palindromes	Java			Advanced	120
	Similar Strings	Java			Advanced	85
	Save Humanity	Java			Expert	100
	Find Strings	Java			Expert	100
	Palindromic Border	Java			Expert	100
	Two Two	Java			Advanced	150
	Two Strings Game	Java			Expert	100
	Letter Islands	Java			Expert	100
	Pseudo-Isomorphic Substrings	Java			Expert	100
	How Many Substrings?	Java			Expert	100

Sorting

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Intro to Tutorial Challenges	Java C#	O(n)	O(1)	Easy	30
	Insertion Sort - Part 1	Java C#	O(n)	O(1)	Easy	30
	Insertion Sort - Part 2	Java C#	O(n^2)	O(1)	Easy	30
	Correctness and the Loop Invariant	Java C#	O(n^2)	O(1)	Easy	30
	Running Time of Algorithms	Java C#	O(n^2)	O(1)	Easy	30
	Quicksort 1 - Partition	Java C#	O(n)	O(n)	Easy	10
	Quicksort 2 - Sorting	Java C#	O(n^2)	O(n)	Easy	30
	Quicksort In-Place	Java	O(n^2)	O(log(n))	Medium	35
	Running Time of Quicksort	Java	O(n log(n))	O(log(n))	Easy	35
	Counting Sort 1	Java C#	O(n+k)	O(k)	Easy	30	value of k in this problem is 100
	Counting Sort 2	Java C#	O(n+k)	O(n+k)	Easy	30	Value of k is 100 in this problem.
	Counting Sort 3	Java	O(n+k)	O(k)	Easy	30
	The Full Counting Sort	Java C#	O(n+k)	O(n+k)	Medium	40
	Closest Numbers	Java C#	O(n log(n))	O(n)	Easy	35
	Find the Median	Java C#	O(n log(n))	O(n)	Easy	35
	Insertion Sort Advanced Analysis	Java			Advanced	50
	Fraudulent Activity Notifications	Java	O(n^2)	O(n)	Medium	40
	Lily's Homework	Java	O(n log(n))	O(n)	Medium	40
	Big Sorting	Java C#	O(n log(n))	O(n)	Easy	20

Search

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Hackerland Radio Transmitters	JS C#	O(n log(n))	O(n)	Medium	25
	Ice Cream Parlor	Java C#	O(n)	O(n)	Easy	30
	Binary Search: Ice Cream Parlor	Java	O(n)	O(n)	Easy	35
	Gridland Metro	Java C#	O(k)	O(k)	Medium	25	k = number of tracks
	Missing Numbers	Java C++ C#	O(n)	O(n)	Easy	45
	Minimum Loss	Java	O(n log(n))	O(n)	Medium	35
	KnightL on a Chessboard	Java			Medium	35
	Pairs	Java C++ C#	O(n log(n))	O(n)	Medium	50
	Sherlock and Array	Java C++ C#	O(n)	O(n)	Easy	40
	Maximum Subarray Sum	Java			Hard	65
	Connected Cells in a grid	Java			Medium	50
	Short Palindrome	Java			Medium	40
	Maximizing Mission Points	Java			Hard	70
	Count Luck	Java			Medium	50
	Cut the Tree	Java			Medium	50
	Making Candies	Java			Hard	45
	Gena Playing Hanoi	Java			Medium	50
	Beautiful Quadruples	Java			Medium	50
	Bike Racers	Java			Hard	65
	Task Scheduling	Java			Advanced	70
	Similar Pair	Java			Advanced	70
	Absolute Element Sums	Java			Hard	70
	Sorted Subsegments	Java			Hard	80
	Distant Pairs	Java			Expert	80
	King Richard's Knights	Java			Hard	80

Graph Theory

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Roads and Libraries	Java			Medium	30
	Synchronous Shopping	Java			Medium	40
	Crab Graphs	Java			Medium	50
	Even Tree	Java			Medium	50
	Snakes and Ladders: The Quickest Way Up	Java			Medium	50
	Subset Component	Java			Hard	50
	Journey to the Moon	Java Python3	O(n + i)	O(n)	Medium	50
	Kruskal (MST): Really Special Subtree	Java			Hard	50
	Minimum Penalty Path	Java			Medium	50
	Demanding Money	Java			Hard	50
	The Story of a Tree	Java			Medium	50
	Breadth First Search: Shortest Reach	Java			Medium	55
	The Value of Friendship	Java			Hard	55
	Clique	Java			Medium	60
	Dijkstra: Shortest Reach 2	Java			Hard	60
	Prim's (MST) : Special Subtree	Java			Medium	60
	Roads in Hackerland	Java			Medium	60
	Toll Cost Digits	Java			Hard	60
	Real Estate Broker	Java			Hard	60
	Matrix	Java			Hard	70
	Bead Ornaments	Java			Advanced	70
	Rust & Murderer	Java	O(n+m)	O(n)	Medium	70
	Recording Episodes	Java			Hard	70
	Kingdom Connectivity	Java			Hard	75
	Journey Scheduling	Java			Hard	75
	Floyd : City of Blinding Lights	Java			Hard	75
	Find the Path	Java			Hard	75
	Repair Roads	Java			Hard	80
	Problem solving	Java			Hard	80
	Computer Game	Java			Hard	80
	Jack goes to Rapture	Java			Medium	80
	Jim and his LAN Party	Java			Hard	80
	Jeanie's Route	Java			Medium	80
	Travel in HackerLand	Java			Hard	80
	Jogging Cats	Java			Advanced	80
	Tree Flow	Java			Hard	80
	Tripartite Matching	Java			Hard	80
	Jumping Rooks	Java			Advanced	80
	Minimum MST Graph	Java			Expert	80
	Coprime Paths	Java			Expert	80
	DAG Queries	Java			Expert	80
	Liars	Java			Advanced	85
	ByteLandianTours	Java			Hard	90
	Kth Ancestor	Java			Hard	90
	Drive	Java			Expert	90
	Road Network	Java			Expert	90
	Savita And Friends	Java			Hard	90
	Favorite sequence	Java			Advanced	95
	Quadrant Queries	Java			Advanced	100
	Going to the Office	Java			Expert	100
	Ticket	Java			Expert	100
	HackerX	Java			Hard	100
	Hacker Country	Java			Hard	100
	Travelling Salesman in a Grid	Java			Expert	100
	Huarongdao	Java			Expert	100
	Vertical Paths	Java			Expert	100
	DFS Edges	Java			Expert	100
	Tree Splitting	Java			Advanced	100
	Definite Random Walks	Java			Expert	100
	Diameter Minimization	Java			Expert	100
	Training the army	Java			Hard	120
	Alex vs Fedor	Java			Expert	150

Greedy

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Minimum Absolute Difference in an Array	Java JS C#	O(n log(n))	O(n)	Easy	15
	Chief Hopper	Java	O(n)	O(n)	Hard	65
	Mark and Toys	Java JS	O(n log(n))	O(n)	Easy	35
	Marc's Cakewalk	Java C#	O(n + k)	O(k)	Easy	15
	Grid Challenge	Java	O(n*(n log (n)))	O(n^2)	Easy	20
	Luck Balance	Java	O(n log(n))	O(1)	Easy	20
	Maximum Perimeter Triangle	Java	O(n log (n))	O(n)	Easy	20
	Permuting Two Arrays	Java JS	O(n log (n))	O(n)	Easy	40
	Jim and the Orders	Java	O(n log (n))	O(n)	Easy	40
	Equal Stacks	Java	O(n)	O(n)	Easy	25
	Sherlock and The Beast	Java	O(n)	O(n)	Easy	30
	Priyanka and Toys	Java JS	O(n log(n))	O(n)	Easy	30
	Largest Permutation	JS	O(n)	O(n)	Easy	30
	Beautiful Pairs	Java			Easy	30
	Yet Another Minimax Problem	Java			Medium	20
	Flipping the Matrix	Java	O(n^2)	O(n^2)	Medium	30
	Roads and Libraries	Java			Medium	30
	Greedy Florist	JS	O(n log (n))	O(n)	Medium	35
	Mark and Toys	Java	O(n log(n))	O(n)	Easy	35
	Max Min	Java	O(n log(n))	O(1)	Medium	35
	Permuting Two Arrays	Java			Easy	40
	Jim and the Orders	Java			Easy	40
	Goodland Electricity	Java			Medium	40
	Fun Game	Java			Medium	40
	Reverse Shuffle Merge	Java			Advanced	50
	Cutting Boards	Java			Hard	60
	Algorithmic Crush	Java			Hard	60
	Prim's (MST): Special Subtree	Java			Medium	60
	Accessory Collection	Java			Hard	60
	Chief Hopper	Java	O(n)	O(n)	Hard	65
	Sherlock and MiniMax	Java			Hard	70
	Team Formation	Java			Advanced	70

Dynamic Programming

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Equal	Java			Medium	30
	Cut Tree	Java			Medium	40
	Mr K marsh	Java			Medium	40
	Sam and sub-strings	Java			Medium	40
	Summing Pieces	Java			Medium	40
	Short Palindrome	Java			Medium	40
	Abbreviation	Java			Medium	40
	Fair Cut	Java			Medium	40
	Fibonacci Modified	Java			Medium	45
	Lego Blocks	Java			Medium	50
	Candies	Java			Medium	50
	Stock Maximize	Java			Medium	50
	Angry Childtren 2	Java			Hard	50
	The Maximum Subarray	Java			Medium	50
	Sherlock and Cost	Java			Medium	50
	Xor and Sum	Java			Medium	50
	Counting Special Sub-Cubes	Java			Medium	50
	Two Robots	Java			Medium	50
	Kingdom Division	Java			Medium	50
	Prime XOR	Java			Medium	50
	HackerRank City	Java			Medium	50
	Nikita and the Game	Java			Medium	50
	Prime Digit Sums	Java			Medium	50
	Mandragora Forest	Java			Medium	50
	LCS Returns	Java			Medium	50
	Grid Walking	Java			Medium	55
	Bricks Game	Java			Medium	55
	The Longest Common Subsequence	Java			Medium	55
	Substring Diff	Java			Medium	60
	Brick Tiling	Java			Hard	60
	Alien Languages	Java			Hard	60
	The Longest Increasing Subsequence	Java			Advanced	60
	The Coin Change Problem	Python3	O(N*M)	O(N)	Hard	60
	Knapsack	Java			Medium	60
	Sherlock's Array Merging Algorithm	Java			Hard	60
	New Year Game	Java			Medium	60
	Shashank and the Palindromic Strings	Java			Advanced	60
	Decibinary Numbers	Java			Hard	60
	Choosing White Balls	Java			Hard	60
	DP: Coin Change	Java			Hard	60
	Clues on a Binary Path	Java			Hard	60
	GCD Matrix	Java			Hard	60
	Coin on the Table	Java			Medium	65
	Interval Selection	Java			Medium	65
	Red John is Back	Java			Medium	65
	Play with words	Java			Medium	65
	Queens on Board	Java			Hard	70
	String Reduction	Java			Hard	70
	Far Vertices	Java			Hard	70
	The Indian Job	Java			Medium	70
	Hexagonal Grid	Java			Hard	70
	Longest Palindromic Subsequence	Java			Hard	70
	Turn Off the Lights	Java			Hard	70
	Tara's Beautiful Permutations	Java			Hard	70
	Two Subarrays	Java			Expert	70
	Mining	Java			Advanced	75
	The Longest Common Subsequence (LCS)	Java			Hard	75
	Points in a Plane	Java			Advanced	80
	Fairy Chess	Java			Advanced	80
	Billboards	Java			Advanced	80
	Requirement	Java			Advanced	80
	A Super Hero	Java			Hard	80
	Covering the stains	Java			Hard	80
	Superman Celebrates Diwali	Java			Hard	80
	Wet Shark and Two Subsequences	Java			Medium	80
	Zurikela's Graph	Java			Hard	80
	New Year Present	Java			Hard	80
	Suffix Rotation	Java			Expert	80
	Black and White Tree	Java			Hard	80
	Beautiful Strings	Java			Hard	80
	Longest Mod Path	Java			Hard	80
	Super Functional Strings	Java			Advanced	80
	Kitty's Calculations on a Tree	Java			Advanced	80
	Liars	Java			Advanced	85
	Dorsey Thief	Java			Advanced	85
	Swap Permutation	Java			Medium	85
	Candles Counting	Java			Medium	85
	Square Subsequences	Java			Hard	90
	Hyper Strings	Java			Advanced	90
	Unique Divide And Conquer	Java			Advanced	90
	Super Kth LIS	Java			Advanced	90
	Counting Road Networks	Java			Expert	90
	Lucky Numbers	Java			Expert	100
	Count Scorecards	Java			Expert	100
	Unfair Game	Java			Advanced	100
	Oil Well	Java			Hard	100
	Modify The Sequence	Java			Advanced	100
	Divisible Numbers	Java			Expert	100
	Ones and Twos	Java			Hard	100
	Extremum Permutations	Java			Medium	100
	Tree Pruning	Java			Advanced	100
	P-sequences	Java			Hard	100
	Best spot	Java			Advanced	100
	Find the Seed	Java			Advanced	100
	The Blacklist	Java			Advanced	100
	Police Operation	Java			Hard	100
	Road Maintenance	Java			Hard	100
	King and Four Sons	Java			Expert	100
	Counting the Ways	Java			Expert	100
	Hard Disk Drives	Java			Expert	100
	Travel around the world	Java			Medium	120
	Robot	Java			Advanced	120
	Vim War	Java			Advanced	120
	Dortmund Dilemma	Java			Advanced	150
	Separate the chocolate	Java			Expert	250

Constructive Algorithms

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Lena Sort	Java			Medium	30
	Flipping the Matrix	Java	O(n^2)	O(n^2)	Medium	30
	Gaming Array	Java			Medium	35
	New Year Chaos	Java			Medium	40
	Bonetrousle	Java			Medium	50
	Yet Another KMP Problem	Java			Hard	60
	Beautiful 3 Set	Java			Hard	60
	Inverse RMQ	Java			Hard	60
	Two Subarrays	Java			Expert	70
	Lovely Triplets	Java			Advanced	80
	Array Construction	Java			Advanced	80

Bit Manipulation

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Lonely Integer	Java	O(n)	O(1)	Easy	20
	Maximizing XOR	Java			Easy	30
	Counter game	Java			Medium	30
	Xor-sequence	Java			Medium	40
	Sum vs XOR	Java	O(n log(n))	O(1)	Easy	20
	The Great XOR	Java			Medium	25
	Flipping bits	Java			Easy	40
	Yet Another Minimax Problem	Java			Medium	30
	Sansa and XOR	Java			Medium	30
	AND Product	Java			Medium	40
	Xoring Ninja	Java			Hard	55
	Cipher	Java			Medium	50
	XOR Matrix	Java			Hard	50
	What's Next?	Java			Medium	50
	String Transmission	Java			Hard	60
	A or B	Java			Medium	50
	Manipulative Numbers	Java			Hard	55
	Stone game	Java			Hard	70
	2's complement	Java			Advanced	70
	Changing Bits	Java			Advanced	70
	XOR key	Java			Advanced	80
	Maximizing the Function	Java			Hard	70
	XOR Subsequences	Java			Advanced	80
	Iterate It	Java			Expert	90
	Hamming Distance	Java			Expert	150
	Mixing proteins	Java			Hard	80

Recursion

#	Title	Solution	Time	Space	Difficulty	Points	Note
	The Power Sum	Java			Easy	20
	Crossword Puzzle	Java			Medium	30
	Recursive Digit Sum	Java			Medium	30
	Simplified Chess Engine	Java			Medium	40
	Password Cracker	Java			Medium	40
	Artithmetic Expressions	Java			Hard	40
	K Factorization	Java			Hard	50
	Bowling Pins	Java			Advanced	60
	Simplified Chess Engine II	Java			Hard	60
	Repetitive K-Sums	Java			Advanced	150

Game Theory

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Game of Stones	JS	O(n)	O(1)	Easy	15
	Tower Breakers	Java			Easy	15
	A Chessboard Game	Java			Easy	15
	Introduction to Nim Game	Java			Easy	15
	Misère Nim	Java			Easy	20
	Nimble Game	Java			Easy	20
	Alice and Bob's Silly Game	Java			Medium	30
	Poker Nim	Java			Easy	20
	Tower Breakers, Revisited!	Java			Medium	25
	Tower Breakers, Again!	Java			Medium	30
	Zero-Move Nim	Java			Medium	50
	Chessboard Game, Again!	Java			Medium	30
	Digits Square Board	Java			Medium	35
	Fun Game	Java			Medium	40
	Stone Division	Java			Hard	50
	Chocolate in Box	Java			Medium	70
	Kitty and Katty	Java			Medium	80
	Powers Game	Java			Medium	50
	Deforestation	Java			Medium	50
	Bob and Ben	Java			Medium	50
	Tower Breakers - The Final Battle	Java			Medium	50
	Simple Game	Java			Hard	60
	Permutation game	Java			Medium	70
	Move the Coins	Java			Hard	60
	Play on benders	Java			Medium	70
	New Year Game	Java			Medium	60
	Stone Piles	Java			Hard	80
	Chocolate Game	Java			Hard	90
	Manasa and Prime game	Java			Hard	90
	Vertical Rooks	Java			Medium	90
	A stones game	Java			Medium	90
	Tastes Like Winning	Java			Expert	100

NP Complete

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Walking the Approximate Longest Path	Java			Hard	70
	Sam's Puzzle (Approximate)	Java			Advanced	85
	Spies, Revised	Java			Expert	100
	TBS Problem	Java			Expert	100

Object Oriented Programming

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Class vs. Instance	Java	N/A	N/A	Easy	30
	Inheritance	Java	O(n)	O(1)	Easy	30
	Abstract Classes	Java	N/A	N/A	Easy	30
	Complex Numbers	Java	O(1)	O(1)	Easy	30

Arrays

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Arrays - DS	C++	O(n)	O(n)	Easy	10
	2D Array - DS	C++	O(1)	O(1)	Easy	15
	Sparse Arrays	C#	O(n + q)	O(n + q)	Medium	25	n = number of input strings, q = number of queries
	Dynamic Array	C#	O(q)	O(n)	Easy	15	q = Number of queries

Linked Lists

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Print the Elements of a Linked List	C++	O(n)	O(1)	Easy	5
	Reverse a Linked List	Java	O(n)	O(1)	Easy	5
	Compare Two Linked Lists	C++	O(n)	O(1)	Easy	5
	Delete a node	C++	O(n)	O(1)	Easy	5

Trees

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Tree: Preorder Traversal	C++	O(n)	O(n)	Easy	10
	Swap Nodes [Algo]	C#	O(n)	O(n)	Medium	40

Balanced Trees

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Self Balancing Tree	C++	O(log(n))	O(n)	Medium	50

Stacks

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Maximum Element	C++	Push-O(1), Delete - O(n), Print - O(1)	Push - O(1), Delete - O(1), Print - O(1)	Easy	20
	Balanced Brackets	Java	O(n)	O(n)	Medium	25

Queues

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Queue using Two Stacks	C#	Enqueue - O(1), Dequeue - O(n), Print - O(n)	Enqueue - O(1), Dequeue - O(1), Print - O(1)	Medium	30

Heap

#	Title	Solution	Time	Space	Difficulty	Points	Note
	QHEAP1	C#	Insert - O(log(n)), Delete - O(n), Print - O(1)	Insert - O(1), Delete - O(1), Print - O(1)	Easy	25

Disjoint Set

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Spaceholder	C#	O(1)	O(1)	Easy	1

Multiple Choice

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Data Structures MCQ 1	Language Independent	NA	NA	Hard	5
	Data Structures MCQ 2	Language Independent	NA	NA	Hard	5
	Data Structures MCQ 3	Language Independent	NA	NA	Hard	5

Trie

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Contacts	C#	Add - O(L), Find - O(L)	Add - O(L), Find - O(1)	Medium	40	L = Length of a contact name

Advanced

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Spaceholder	C#	O(1)	O(1)	Easy	1

Fundamentals

#	Title	Solution	Time	Space	Difficulty	Points	Note
	Leonardo's Prime Factors	C#	O(1)	O(1)	Easy	10