🧠 📚 ⏱ Java Data Structures and Algorithms

• Implementation of Data Structures and Algorithms.
• Solved Solutions from leetcode ant etc.

Helping welcome! Thanks!

📌 notation keys::

• 🍏 - easy;
• 🍊 - medium;
• 🍎 - hard;
• ⭕️(1), ⭕️log(N), ⭕️(N^2)... - Big O notations;
• [✍🏻] - in progress;
• [🙇🏻‍♂️] - hard to solve;
• [❓] - the solution is not optimal;
• [✔️] - done;
• [🆗] - Test passed Ok;

Data Structure: Arrays

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed:
findMin	🍏	[✔️]	⭕️(N)	[🆗] Open
merge	🍏	[✍🏻]
pop	🍏	[✔️]	⭕️(N)	[🆗] Open
push	🍏	[✔️]	⭕️(N)	[🆗] Open
remove(position)	🍏	[✔️]	⭕️(N)	[🆗] Open
reverse	🍊	[✔️]	⭕️(N)	[🆗] Open
reverse(start, end)	🍊	[✔️]	⭕️(N)
size	🍏	[✔️]	⭕️(N)	[🆗] Open
sort	🍊	[✔️]	⭕️(N^2)	[🆗] Open
GenericArray <T>	🍊

Data Structure: Matrix

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
rotate	🍊	[✔️]	⭕️(N^2)	[🆗] Open
transpose	🍊	[✔️]	⭕️(N^2)	[🆗] Open
reflect	🍊	[✔️]	⭕️(N^2)	[🆗] Open

Data Structure: Singly Linked List

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
append(data)	🍏	[✔️]	⭕️(1)	[🆗] Open
preppend(data)	🍏	[✔️]	⭕️(N)	[🆗] Open
find(data)	🍏	[✔️]	⭕️(N)	[🆗] Open
deleteFirst()	🍏	[✔️]	⭕️(N)	[🆗] Open
deleteLast()	🍏	[✔️]	⭕️(1)	[🆗] Open
deletePos(position)	🍏	[✔️]	⭕️(N)	[🆗] Open
length()	🍏	[✔️]	⭕️(N)	[🆗] Open
reverse()	🍏	[✔️]	⭕️(N^2)	[🆗] Open
getMid(LinkedList)	🍏	[✔️]	⭕️(N)	[🆗] Open
merge(LinkedList, LinkedList)	🍊	[✔️]	⭕️(N)	[🆗] Open
sort()	🍊	[✔️]	⭕️(N Log(N))	[🆗] Open

Data Structure: Doubly Linked List

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
append(data)	🍏	[✔️]	⭕️(1)	[🆗] Open
preppend(data)	🍏	[✔️]	⭕️(1)	[🆗] Open
deleteFirst()	🍏	[✔️]	⭕️(1)	[🆗] Open
deleteLast()	🍏	[✔️]	⭕️(1)	[🆗] Open

Data Structure: Stack<Listnode>

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
getMin()	🍏	[✔️]	⭕️(N)	[🆗] Open
peak()	🍏	[✔️]	⭕️(1)	[🆗] Open
pop()	🍏	[✔️]	⭕️(1)	[🆗] Open
push(data)	🍏	[✔️]	⭕️(1)	[🆗] Open

Data Structure: Queue

Algorithm (operation)	Level	Done	Big ⭕️ Notation
isEmpty	🍏	[✍🏻]
peak	🍏	[✍🏻]
enqueue	🍏	[✍🏻]
dequeue	🍏	[✍🏻]

Data Structure: Hash Table<Listnode>

Algorithm (operation)	Level	Done	Big ⭕️ Notation
hash(key)	🍏	[✍🏻]
set(key, value)	🍏	[✍🏻]
delete(key)	🍏	[✍🏻]
get(key)	🍏	[✍🏻]
has(key)	🍏	[✍🏻]
getKeys()	🍏	[✍🏻]
getValues()	🍏	[✍🏻]

Data Structure: Heap

Algorithm (operation)	Level	Done	Big ⭕️ Notation
add	🍎	[✍🏻]
remove	🍎	[✍🏻]

Data Structure: Trie

Algorithm (operation)	Level	Done	Big ⭕️ Notation
addWord	🍎	[✍🏻]
deleteWord	🍎	[✍🏻]

Data Structure: Tree

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
Binary Tree	🍎	[✍🏻]
Binary Tree Recursive: insert(data)	🍎	[✔️]	⭕️log(N)	[🆗] Open
Binary Tree Recursive: preOrderPrint()	🍎	[✔️]	⭕️log(N)	[🆗] Open
Binary Tree Recursive: inOrderPrint()	🍎	[✔️]	⭕️log(N)	[🆗] Open
Binary Tree Recursive: postOrderPrint()	🍎	[✔️]	⭕️log(N)	[🆗] Open
Binary Tree Recursive: find(data)	🍎	[✔️]	⭕️log(N)	[🆗] Open
Binary Tree Recursive: delete()	🍎	[✔️]	⭕️log(N)	[🆗] Open
Binary Tree Iterative: insert(data)	🍎	[✔️]	⭕️(N)	[🆗] Open
Binary Tree Iterative: preOrderPrint()	🍎	[✔️]	⭕️(N)	[🆗] Open
Binary Tree Iterative: inOrderPrint()	🍎	[✔️]	⭕️(N)	[🆗] Open
Binary Tree Iterative: postOrderPrint()	🍎	[✔️]	⭕️(N)	[🆗] Open
AVL Tree	🍎	[✍🏻]
Fenwick Tree	🍎	[✍🏻]
Red-Black Tree	🍎	[✍🏻]
Segment Tree	🍎	[✍🏻]

• Data Structure: Graph

Algorithm (operation)	Level	Done	Big ⭕️ Notation
directed	🍎	[✍🏻]
undirected	🍎	[✍🏻]

• Data Structure: Search

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
Binary Search Iterative	🍊	[✔️]	⭕️(N)	[🆗] Open
Binary Search Recursive	🍊	[✔️]	⭕️(log N)	[🆗] Open

• Data Structure: Sorting

Algorithm (operation)	Level	Done	Big ⭕️ Notation	Tests passed
Buble Sort <T>	🍏	[✔️]	⭕️(N^2)	[🆗] Open
Quick Sort	🍊	[✔️]	⭕️(N^2)	[🆗] Open
MergeSort	🍏	[✔️]	⭕️(N log(N))	[🆗] Open
Insertion Sort	🍏	[✔️]	⭕️(N^2)	[🆗] Open

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Leetcode's Problems by Skills:

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Arrays

Arrays SubSkills	Lvl	Complexity: Time , Space	Solved Problems
Elements Sum	🍏	⏱ ⭕️(N^2), 💾 ⭕️(N)	1. Two Sum
Duplicates Remove	🍏	⏱ ⭕️(N), 💾 ⭕️(1)	26. Remove Duplicates from Sorted Array
Element Search	🍏	⏱ ⭕️(N), 💾 ⭕️(1)	35. Search Insert Position
Elements Sort	🍏	⏱ ⭕️(N^2), 💾 ⭕️(1)	88. Merge Sorted Array
Elements Memoization	🍏	⏱ ⭕️(N), 💾 ⭕️(1)	121. Best Time to Buy and Sell Stock
Elements Move	🍏	⏱ ⭕️(N), 💾 ⭕️(1)	283. Move Zeroes
Elements Sort , Math	🍏	⏱ ⭕️(N^2), 💾 ⭕️(1)	977. Squares of a sorted Array
Element Two Pointers	🍊	⏱ ⭕️(N), 💾 ⭕️(1)	11. Container with Most Water
Permutations	🍊	⏱ ⭕️(N^2), 💾 ⭕️(1)	31. Next Permutation
Backtracking	🍊	⏱ ⭕️(N^2), 💾 ⭕️(N)	46. Permutations
Matrix Operations	🍊	⏱ ⭕️(N^2), 💾 ⭕️(1)	48. Rotate Image
Elements Math	🍊	⏱ ⭕️(N), 💾 ⭕️(1)	53. Maximum Subarray
Elements Sort	🍊	⏱ ⭕️(N^2), 💾 ⭕️(N^2)	56. Merge Intervals
Two Pointers	🍊	⏱ ⭕️(N), 💾 ⭕️(N)	167. Two Sum II
Two Pointers	🍊	⏱ ⭕️(N), 💾 ⭕️(N)	189. Rotate Array
DP	🍊	⏱ ⭕️(N), 💾 ⭕️(1)	198. House Robber
Elements Sort	🍎	⏱ ⭕️(log(N)), 💾 ⭕️(1)	4. Median of Two Sorted Arrays

Backtracking

Backtracking SubSkills	Lvl	Complexity: Time , Space	Solved Problems
Hash Table	🍊	⏱ ⭕️(N), 💾 ⭕️(N)	17. Letter Combinations of a Phone Number
Recursion	🍊	⏱ ⭕️(N^2), 💾 ⭕️(N)	22. Generate Parentheses
String, Recursion	🍊	⏱ ⭕️(N^2), 💾 ⭕️(N)	39. Combination Sum
Recursion	🍊	⏱ ⭕️(N^2), 💾 ⭕️(2N)	77. Combinations
Matrix, Recursion	🍊	⏱ ⭕️(N^2), 💾 ⭕️(N^2)	79. Word Search
String, Recursion	🍊	⏱ ⭕️(N^2), 💾 ⭕️(N)	784. Letter Case Permutation

Binary Search

Skills by abc	Diff	Language	Solved Problems
Binary Search	🍏 easy	Java	367. Valid Perfect Square
Binary Search	🍊 medium	Java	33. Search In Rotated Sorted Array
Binary Search	🍊 medium	Java	34. Find First and Last Position of Element in Sorted Array
Binary Search	🍊 medium	Java	153. Find Minimum in Rotated Sorted Array
Binary Search	🍊 medium	Java	167. Two Sum II
Binary Search	🍎 hard	Java	4. Median of Two Sorted Arrays
➿	➿	➿	➿
Binary Tree	🍏 easy	Java	94. Binary Tree Inorder Traversal
Binary Tree	🍏 easy	Java	100. Same Tree
Binary Tree	🍏 easy	Java	101. Symmetric Tree
Binary Tree	🍏 easy	Java	104. Maximum Depth of Binary Tree
Binary Tree	🍏 easy	Java	108. Convert Sorted Array To Binary Search Tree
Binary Tree	🍏 easy	Java	145. Binary Tree Postorder Traversal
Binary Tree	🍏 easy	Java	226. Invert Binary Tree
Binary Tree	🍏 easy	Java	543. Diameter of Binary Tree
Binary Tree	🍏 easy	Java	617. Merge Two Binary Trees
Binary Tree	🍊 medium	Java	98. Validate Binary Search Tree
Binary Tree	🍊 medium	Java	102. Binary Tree Level Order Traversal
Binary Tree	🍊 medium	Java	105. Construct Binary Tree from Preorder and Inorder Traversal
Binary Tree	🍊 medium	Java	114. Flatten Binary Tree to Linked List
Binary Tree	🍊 medium	Java	116. Populating Next Right Pointers in Each Node
Binary Tree	🍊 medium	Java	199. Binary Tree Right Side View
Binary Tree	🍊 medium	Java	669. Trim a Binary Search Tree
➿	➿	➿	➿
Bit Manipulation	🍏 easy	Java	67. Add Binary
Bit Manipulation	🍏 easy	Java	136. Single Number
Bit Manipulation	🍏 easy	Java	191. Number of 1 Bits
Bit Manipulation	🍏 easy	Java	338. Counting Bits
➿	➿	➿	➿
Breadth-First Search	🍊 medium	Java	116. Populating Next Right Pointers in Each Node
Breadth-First Search	🍊 medium	Java	994. Rotting Oranges
➿	➿	➿	➿
Design	🍏 easy	Java	155. Min Stack
➿	➿	➿	➿
Depth-First Search	🍏 easy	Java	733. Flood Fill
Depth-First Search	🍊 medium	Java	98. Validate Binary Search Tree
Depth-First Search	🍊 medium	Java	695. Max Area of Islands
➿	➿	➿	➿
Divide and Conquer	🍏 easy	Java	190. Reverse Bits
Divide and Conquer	🍎 hard	Java	4. Median of Two Sorted Arrays
➿	➿	➿	➿
Dynamic Programming	🍏 easy	Java	70. Climbing Stairs
Dynamic Programming	🍏 easy	Java	118. Pascal's Triangle
Dynamic Programming	🍏 easy	Java	119. Pascal's Triangle II
Dynamic Programming	🍏 easy	Java	121. Best Time to Buy and Sell Stock
Dynamic Programming	🍏 easy	Java	509. Fibonacci Number
Dynamic Programming	🍊 medium	Java	5. Longest Palindromic Substring
Dynamic Programming	🍊 medium	Java	53. Maximum Subarray
Dynamic Programming	🍊 medium	Java	62. Unique Paths
Dynamic Programming	🍊 medium	Java	63. Unique Paths II
Dynamic Programming	🍊 medium	Java	97. Interleaving String
Dynamic Programming	🍊 medium	Java	198. House Robber
Dynamic Programming	🍊 medium	Java	322. Coin Change
Dynamic Programming	🍊 medium	Java	542. 01 Matrix
➿	➿	➿	➿
Hash Table	🍏 easy	Java	1. Two Sum
Hash Table	🍏 easy	Java	13. Roman to Integer
Hash Table	🍏 easy	Java	202. Happy Number
Hash Table	🍏 easy	Java	217. Contains Duplicate
Hash Table	🍏 easy	Java	448. Find All Numbers Disappeared in an Array
Hash Table	🍏 easy	Java	929. Unique Email Addresses
Hash Table	🍊 medium	Java	3. Longest Substring Without Repeating Characters
Hash Table	🍊 medium	Java	49. Group Anagram
Hash Table	🍊 medium	Java	128. Longest Consecutive Sequence
➿	➿	➿	➿
Linked List	🍏 easy	Java	21. Merge Two Sorted Lists
Linked List	🍏 easy	Java	160. Intersection of Two Linked Lists
Linked List	🍏 easy	Java	203. Remove Linked List Elements
Linked List	🍏 easy	Java	206. Reverse Linked List
Linked List	🍏 easy	Java	234. Palindrome Linked List
Linked List	🍏 easy	Java	876. Middle of the Linked List
Linked List	🍊 medium	Java	2. Add Two Numbers
Linked List	🍊 medium	Java	19. Remove Nth Node From End of List
Linked List	🍊 medium	Java	116. Populating Next Right Pointers in Each Node
Linked List	🍊 medium	Java	148. Sort List
Linked List	🍎 hard	Java	23. Merge k Sorted Lists
➿	➿	➿	➿
Math	🍏 easy	Java	7. Reverse Integer
Math	🍏 easy	Java	9. Palindrome Number
Math	🍏 easy	Java	231. Power of Two
Math	🍏 easy	Java	258. Add Digits
Math	🍊 medium	Java	2. Add Two Numbers
➿	➿	➿	➿
Matrix	🍏 easy	Java	733. Flood Fill
Matrix	🍊 medium	Java	48. Rotate Image
Matrix	🍊 medium	Java	695. Max Area of Islands
➿	➿	➿	➿
Memoization	🍏 easy	Java	509. Fibonacci Number
➿	➿	➿	➿
Merge Sort	🍊 medium	Java	148. Sort List
Merge Sort	🍎 hard	Java	Merge k Sorted Lists
➿	➿	➿	➿
Number Theory	🍊 medium	Java	204. Count Primes
➿	➿	➿	➿
Recursion	🍏 easy	Java	21. Merge Two Sorted Lists
Recursion	🍏 easy	Java	191. Number of 1 Bits
Recursion	🍏 easy	Java	206. Reverse Linked List
Recursion	🍏 easy	Java	234. Palindrome Linked List
Recursion	🍏 easy	Java	231. Power of Two
Recursion	🍏 easy	Java	509. Fibonacci Number
Recursion	🍊 medium	Java	2. Add Two Numbers
➿	➿	➿	➿
Sliding Window	🍏 easy	Java	643. Maximum Average Subarray I
Sliding Window	🍊 medium	Java	3. Longest Substring Without Repeating Characters
Sliding Window	🍊 medium	Java	438. Find All Anagrams in a String
Sliding Window	🍊 medium	Java	567. Permutation in String
➿	➿	➿	➿
Stack	🍏 easy	Java	20. Valid Parentheses
Stack	🍏 easy	Java	155. Min Stack
Stack	🍊 medium	Java	394. Decode String
Stack	🍊 medium	Java	1003. Check If Word Is Valid After Substitutions
➿	➿	➿	➿
Sorting	🍏 easy	Java	88. Merge Sorted Array
Sorting	🍏 easy	Java	977. Squares of a sorted Array
Sorting	🍊 medium	Java	56. Merge Intervals
➿	➿	➿	➿
String	🍏 easy	Java	14. Longest Common Prefix
String	🍏 easy	Java	242. Valid Anagram
String	🍏 easy	Java	344. Reverse String
String	🍏 easy	Java	387. First Unique Character in a String
String	🍏 easy	Java	551. Student Attendance Record I
String	🍏 easy	Java	557. Reverse Words in a String III
String	🍏 easy	Java	771. Jewels and Stones
String	🍊 medium	Java	3. Longest Substring Without Repeating Characters
String	🍊 medium	Java	5. Longest Palindromic Substring
String	🍊 medium	Java	567. Permutation in String
String	🍊 medium	Java	784. Letter Case Permutation
➿	➿	➿	➿
Tree	🍏 easy	Java	[ 617. Merge Two Binary Trees
Tree	🍊 medium	Java	116. Populating Next Right Pointers in Each Node
Tree	🍊 medium	Java	687. Longest Unvalued Path
➿	➿	➿	➿
Two Pointers	🍏 easy	Java	125. Valide Palindrome
Two Pointers	🍏 easy	Java	202. Happy Number
Two Pointers	🍏 easy	Java	283. Move Zeroes
Two Pointers	🍏 easy	Java	344. Reverse String
Two Pointers	🍏 easy	Java	392. Is Subsequence
Two Pointers	🍏 easy	Java	557. Reverse Words in a String III
Two Pointers	🍊 medium	Java	11. Container with Most Water
Two Pointers	🍊 medium	Java	19. Remove Nth Node From End of List
Two Pointers	🍊 medium	Java	167. Two Sum II
Two Pointers	🍊 medium	Java	189. Rotate Array
Two Pointers	🍊 medium	Java	567. Permutation in String
➿	➿	➿	➿
Union Find	🍊 medium	Java	200. Number of Islands

need think

• [✔️ Java] 🍊 287. Find the Duplicate Number

HackerRank

• [✔️ Java] A very big sum
• [✔️ Java] Compare the triplets

CodeWars

• [✔️ JS] Build Tower
• [✔️ JS] Camel Case
• [✔️ Java] Counting Duplicates
• [✔️ Java] Help The Book Seller
• [✔️ Java] Simple Encryption
• [✔️ JS] Pete The Baker
• [✔️ Java] Playing With Digits

🛠 Use Unit Tests:

• run all tests

mvn clean test

• and result in the terminal:

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running dataStructures.tree.binarySearchTreeRecursive.BinarySearchTreeRecursiveTest
Test - Binary Search Tree Recursive : insert(data) - passed ok
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.009 sec
Running dataStructures.tree.binarySearchTreeIterative.BinarySearchTreeIterativeTest
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running dataStructures.doublyLinkedList.DoublyLinkedListTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running dataStructures.arrays.ArraysTest
Tests run: 8, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.003 sec
Running dataStructures.arrays.BinarySearchArrayTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running dataStructures.singlyLinkedList.SinglyLinkedListTest
Tests run: 12, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running dataStructures.stack.StackTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running dataStructures.matrix.MatrixTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running sorting.InsertionSortTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running sorting.QuickSortTest
Tests run: 0, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running sorting.BubleSortTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running sorting.MergeSortTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec

Results :

Tests run: 46, Failures: 0, Errors: 0, Skipped: 0