LeetCode Java Solutions

  

Hi 👋, I'm Chee Hwa and welcome to LeetCode Solutions in Java.

As I'm new to LeetCode and progamming in general, I'm practicing everyday and hope to share my solutions and learnings with you.

• Exclusively on Java
• Beginner problems
• Daily Challenge if within my ability

Topics

The problem sets and solutions are grouped into Topics as stated in LeetCode.

• Array
• Binary Search
• Bit Manipulation
• Greedy
• Hash Table
• Heap (Priority Queue)
• Math
• Matrix
• Simulation
• Sorting
• String
• Two Pointers

---

Array

#	Problem	Solution	Difficulty	Topics	Note
393	UTF-8 Validation	Java without, or with Bit Manipulation	Medium	Array, Bit Manipulation
485	Maximum Consecutive Ones	Java	Easy	Array
609	Find Duplicate File in System	Java	Medium	Array, Hash Table, String
948	Bag of Tokens	Java	Medium	Array, Greedy, Sorting, Two Pointers
985	Sum of Even Numbers After Queries	Java	Medium	Array, Simulation
1337	The K Weakest Rows in a Matrix	Java with Heap (Priority Queue) or Sorting	Easy	Array, Binary Search, Heap (Priority Queue), Matrix, Sorting
2007	Find Original Array From Doubled Array	Java with Hash Table, Queue or Counting Array	Medium	Array, Greedy, Hash Table, Sorting

⬆️Back To Top

Binary Search

#	Problem	Solution	Difficulty	Topics	Note
1337	The K Weakest Rows in a Matrix	Java with Heap (Priority Queue) or Sorting	Easy	Array, Binary Search, Heap (Priority Queue), Matrix, Sorting	Solution Using Linear Search

⬆️Back To Top

Bit Manipulation

#	Problem	Solution	Difficulty	Topics	Note
393	UTF-8 Validation	Java	Medium	Array, Bit Manipulation
1342	Number of Steps to Reduce a Number to Zero	Java	Easy	Bit Manipulation, Math	Solution Using Math
1680	Concatenation of Consecutive Binary Numbers	Java	Medium	Bit Manipulation, Math, Simulation	Solution Using Math

⬆️Back To Top

Greedy

#	Problem	Solution	Difficulty	Topics	Note
948	Bag of Tokens	Java	Medium	Array, Greedy, Sorting, Two Pointers
2007	Find Original Array From Doubled Array	Java with Hash Table, Queue or Counting Array	Medium	Array, Greedy, Hash Table, Sorting

⬆️Back To Top

Hash Table

#	Problem	Solution	Difficulty	Topics	Note
12	Integer to Roman	Java	Medium	Hash Table, Math, String
13	Roman to Integer	Java	Easy	Hash Table, Math, String	Solution Without Hash Table
609	Find Duplicate File in System	Java	Medium	Array, Hash Table, String
2007	Find Original Array From Doubled Array	Java	Medium	Array, Greedy, Hash Table, Sorting	Solution Using Queue or Counting Array

⬆️Back To Top

Heap (Priority Queue)

#	Problem	Solution	Difficulty	Topics	Note
1337	The K Weakest Rows in a Matrix	Java	Easy	Array, Binary Search, Heap (Priority Queue), Matrix, Sorting	Solution Using Sorting

⬆️Back To Top

Math

#	Problem	Solution	Difficulty	Topics	Note
12	Integer to Roman	Java	Medium	Hash Table, Math, String
13	Roman to Integer	Java	Easy	Hash Table, Math, String	Solution Using Hash Table
412	Fizz Buzz	Java	Easy	Math, Simulation, String
1342	Number of Steps to Reduce a Number to Zero	Java	Easy	Bit Manipulation, Math	Solution Using Bit Manipulation
1680	Concatenation of Consecutive Binary Numbers	Java	Medium	Bit Manipulation, Math, Simulation	Solution Using Bit Manipulation

⬆️Back To Top

Matrix

#	Problem	Solution	Difficulty	Topics	Note
1337	The K Weakest Rows in a Matrix	Java with Heap (Priority Queue) or Sorting	Easy	Array, Binary Search, Heap (Priority Queue), Matrix, Sorting

⬆️Back To Top

Simulation

#	Problem	Solution	Difficulty	Topics	Note
412	Fizz Buzz	Java	Easy	Math, Simulation, String
985	Sum of Even Numbers After Queries	Java	Medium	Array, Simulation
1680	Concatenation of Consecutive Binary Numbers	Java with Bit Manipulation or Math	Medium	Bit Manipulation, Math, Simulation

⬆️Back To Top

Sorting

#	Problem	Solution	Difficulty	Topics	Note
948	Bag of Tokens	Java	Medium	Array, Greedy, Sorting, Two Pointers
1337	The K Weakest Rows in a Matrix	Java	Easy	Array, Binary Search, Heap (Priority Queue), Matrix, Sorting	Solution Using Heap (Priority Queue)
2007	Find Original Array From Doubled Array	Java with Hash Table or Queue	Medium	Array, Greedy, Hash Table, Sorting	Solution Using Counting Array

⬆️Back To Top

String

#	Problem	Solution	Difficulty	Topics	Note
12	Integer to Roman	Java	Medium	Hash Table, Math, String
13	Roman to Integer	Java	Easy	Hash Table, Math, String	Solution Using Hash Table
412	Fizz Buzz	Java	Easy	Math, Simulation, String
609	Find Duplicate File in System	Java	Medium	Array, Hash Table, String

⬆️Back To Top

Two Pointers

#	Problem	Solution	Difficulty	Topics	Note
948	Bag of Tokens	Java	Medium	Array, Greedy, Sorting, Two Pointers

⬆️Back To Top