LeetCode 75 Solutions in Java

This repository contains solutions to LeetCode's 75 Essential & Trending Problems, all implemented in Java.

Must-do problem list for interview prep: The problems selected in this repository are curated based on their frequency of appearance in technical interviews and their relevance in assessing a candidate's problem-solving skills. Mastering these problems can significantly boost your chances of success in coding interviews.

Best for 1~3 month of prep time: Whether you're gearing up for a new job hunt or just looking to brush up on your algorithm skills, this collection of problems is optimally designed to be tackled over a period of one to three months. This duration allows for both in-depth understanding and regular practice, ensuring that you're well-prepared and confident in your problem-solving abilities.

Feel free to explore, practice, and ace your upcoming interviews!

Table of Contents

• Problems and Solutions
• Usage
• Contribution
• Content Rights
• License

Problems and Solutions

Category	Problem	Solution	Difficulty
Array / String	Merge Strings Alternately	MergeStringsAlternately.java	Easy
Array / String	Greatest Common Divisor of Strings	GreatestCommonDivisorOfStrings.java	Easy
Array / String	Kids With the Greatest Number of Candies	GreatestNumberOfCandies.java	Easy
Array / String	Can Place Flowers	CanPlaceFlowers.java	Easy
Array / String	Reverse Vowels of a String	ReverseVowelsOfString.java	Easy
Array / String	Reverse Words in a String	ReverseWordsInString.java	Medium
Array / String	Product of Array Except Self	ProductExceptSelf.java	Medium
Array / String	Increasing Triplet Subsequence	IncreasingTriplet.java	Medium
Array / String	String Compression	StringCompressor.java	Medium
Two Pointers	Move Zeroes	ZeroMover.java	Easy
Two Pointers	Is Subsequence	SubsequenceChecker.java	Easy
Two Pointers	Container With Most Water	WaterContainer.java	Medium
Two Pointers	Max Number of K-Sum Pairs	MaxOperationsCounter.java	Medium
Sliding Window	Maximum Average Subarray I	MaxAverageSubarrayCalculator.java	Easy
Sliding Window	Maximum Number of Vowels in a Substring of Given Length	MaxVowelSubstringCalculator.java	Medium
Sliding Window	Max Consecutive Ones III	BinaryArrayMaxOnesCalculator.java	Medium
Sliding Window	Longest Subarray of 1's After Deleting One Element	BinarySubarrayCalculator.java	Medium
Prefix Sum	Find the Highest Altitude	AltitudeCalculator.java	Easy
Prefix Sum	Find Pivot Index	PivotFinder.java	Easy
Hash Map / Set	Find the Difference of Two Arrays	ArraysDifferenceFinder.java	Easy
Hash Map / Set	Unique Number of Occurrences	UniqueOccurrenceChecker.java	Easy
Hash Map / Set	Determine if Two Strings Are Close	StringCloseChecker.java	Medium
Hash Map / Set	Equal Row and Column Pairs	MatrixPairs.java	Medium
Stack	Decode String	StringDecoder.java	Medium
Stack	Asteroid Collision	AsteroidCollisionSimulator.java	Medium
Stack	Removing Stars From a String	StarStringProcessor.java	Medium
Queue	Number of Recent Calls	RecentCounter.java	Easy
Queue	Dota2 Senate	SenateDecisionSimulator.java	Medium
Linked List	Delete the Middle Node of a Linked List	LinkedListProcessor.java	Medium
Linked List	Odd Even Linked List	OddEvenLinkedListTransformer.java	Medium
Linked List	Reverse Linked List	LinkedListReverser.java	Easy
Linked List	Maximum Twin Sum of a Linked List	MaxTwinSumCalculator.java	Medium
Binary Tree - DFS	Maximum Depth of Binary Tree	BinaryTreeDepthCalculator.java	Easy
Binary Tree - DFS	Leaf-Similar Trees	LeafSimilarTreesChecker.java	Easy
Binary Tree - DFS	Count Good Nodes in Binary Tree	GoodNodeCounter.java	Medium
Binary Tree - DFS	Path Sum III	PathSumCounter.java	Medium
Binary Tree - DFS	Longest ZigZag Path in a Binary Tree	ZigZagPathCalculator.java	Medium
Binary Tree - DFS	Lowest Common Ancestor of a Binary Tree	LowestCommonAncestorFinder.java	Medium
Binary Tree - BFS	Binary Tree Right Side View	RightViewTree.java	Medium
Binary Tree - BFS	Maximum Level Sum of a Binary Tree	MaxLevelSumCalculator.java	Medium
Binary Search Trie	Search in a Binary Search Tree	BSTSearcher.java	Easy
Binary Search Trie	Delete Node in a BST	BSTNodeDeleter.java	Medium
Graphs - DFS	Keys and Rooms	RoomAccessChecker.java	Medium
Graphs - DFS	Number of Provinces	FriendshipCircleFinder.java	Medium
Graphs - DFS	Reorder Routes to Make All Paths Lead to the City Zero	NetworkReorderer.java	Medium
Graphs - DFS	Evaluate Division	EquationCalculator.java	Medium
Graphs - BFS	Nearest Exit from Entrance in Maze	MazeExitFinder.java	Medium
Graphs - BFS	Rotting Oranges	RottenOrangesCalculator.java	Medium
Heap / Priority Queue	Kth Largest Element in an Array	KthLargestElementFinder.java	Medium
Heap / Priority Queue	Smallest Number in Infinite Set	SmallestInfiniteSet.java	Medium
Heap / Priority Queue	Maximum Subsequence Score	MaxScoreCalculator.java	Medium
Heap / Priority Queue	Total Cost to Hire K Workers	HiringCostCalculator.java	Medium
Binary Search	Guess Number Higher or Lower	NumberGuesser.java	Easy
Binary Search	Successful Pairs of Spells and Potions	SpellPotionPairFinder.java	Medium
Binary Search	Find Peak Element	PeakElementFinder.java	Medium
Binary Search	Koko Eating Bananas	BananaEater.java	Medium
Backtracking	Letter Combinations of a Phone Number	PhoneNumberCombinations.java	Medium
Backtracking	Combination Sum III	CombinationSumFinder.java	Medium
DP - 1D	N-th Tribonacci Number	TribonacciCalculator.java	Easy
DP - 1D	Min Cost Climbing Stairs	StairCostCalculator.java	Easy
DP - 1D	House Robber	HouseRobber.java	Medium
DP - 1D	Domino and Tromino Tiling	TilingCalculator.java	Medium
DP - Multidimensional	Unique Paths	GridPathFinder.java	Medium
DP - Multidimensional	Longest Common Subsequence	SubsequenceFinder.java	Medium
DP - Multidimensional	Best Time to Buy and Sell Stock with Transaction Fee	StockTradingProfitCalculator.java	Medium
DP - Multidimensional	Edit Distance	EditDistanceCalculator.java	Medium
Bit Manipulation	Counting Bits	BitCounter.java	Easy
Bit Manipulation	Single Number	UniqueNumberFinder.java	Easy
Bit Manipulation	Minimum Flips to Make a OR b Equal to c	BitFlipCalculator.java	Medium
Trie	Implement Trie (Prefix Tree)	PrefixTrie.java	Medium
Trie	Search Suggestions System	SearchSuggestionsSystem.java	Medium
Intervals	Non-overlapping Intervals	IntervalOverlapRemover.java	Medium
Intervals	Minimum Number of Arrows to Burst Balloons	ArrowBalloonBurstOptimizer.java	Medium
Monotonic Stack	Daily Temperatures	TemperatureChangeCalculator.java	Medium
Monotonic Stack	Online Stock Span	StockPriceSpanCalculator.java	Medium

Usage

1. Clone the repository:

git clone https://github.com/teamlead/leetcode-75-solutions-java.git

2. Navigate to a specific problem:

cd src/category_name

3. Compile and run the Java solution:

javac ProblemName.java
java -ea ProblemName

or if you use Java11+ run the source code file directly, without intermediate compilation:

java -ea ProblemName.java

If using IDEA, right-click the src folder, then select "Mark Directory" as "Sources Root". Now, Java files should benefit from all the Java IDE features of IntelliJ IDEA, including autocomplete, debug, syntax highlighting, and more.

Remember, when using assertions in Java, ensure that you've enabled them by using the -ea flag when running the Java program.

Contribution

Feel free to fork this repository and add your solutions or improvements. Pull requests are welcome!

Content Rights

The problems discussed in this repository are sourced from LeetCode and are Copyrighted Material owned by LeetCode. They are used here for educational purposes only. It is strongly advised not to use them in any other way that might infringe on the intellectual property rights of the original source. Always refer to the original LeetCode link for the complete and most up-to-date problem statement.

License

This project is open source and available under the MIT License.