rajeevranjancom / Leetcode_Java

Leetcode Java Solution and Documentation

Leetcode_Java@Rajeev Ranjan

Solution@Leetcode

Links:

Websites
https://docs.oracle.com/en/java/ (Java Documentation)
https://docs.oracle.com/en/java/javase/15/ (JDK 15 Documentation)
https://docs.oracle.com/javacomponents/ (Java Components)
https://docs.oracle.com/javaee/7/index.html (Java Platform, Enterprise Edition (Java EE) 7)
https://docs.oracle.com/javame/8.3/index.html (Java Platform, Micro Edition Embedded (Java ME Embedded) 8.3)
https://docs.oracle.com/javase/8/javase-embedded.htm (Java Platform, Standard Edition (Java SE) 8)
https://docs.oracle.com/en/java/javacard/3.1/ (Java Card 3.1 Documentation)
https://docs.oracle.com/en/java/javacard/3.1/books.html (Release Notes and Books)
https://docs.oracle.com/en/java/javase/15/docs/api/index.html (Java® Platform, Standard Edition & Java Development Kit
Version 15 API Specification)
https://www.java.com/ES/download/ (Java Download)
https://www.oracle.com/in/java/technologies/javase-downloads.html (Java SE Downloads)

Notes:

Important
Java is a set of computer software and specifications developed by James Gosling at Sun Microsystems, which was later acquired by the Oracle Corporation, that provides a system for developing application software and deploying it in a cross-platform computing environment
Initial release date: 23 January 1996
Developed by: Sun Microsystems
Original author(s) James Gosling, Sun Microsystems
Developer(s) Oracle Corporation
Operating system Microsoft Windows, Solaris, Linux, macOS
Platform IA-32, x64, ARMv7, ARMv8, SPARC (up to Java 14) (Java 8 includes 32-bit support – while no longer supported freely by Oracle for commercial use – 32- bit platforms are not supported in other versions, since dropped officially in Java 10.)
Available in English, Chinese, French, German, Italian, Japanese, Korean, Portuguese, Spanish, Swedish

Table:

Question	Solution	Difficulty	Tag
1. Two Sum	Solution	Easy	Array / Hash Table
2. Add Two Numbers	Solution	Medium	Linked List
3. Longest Substring Without Repeating Characters	Solution	Medium	Hash Table / Two Pointers
4. Median of Two Sorted Arrays	Solution	Hard	Array / Binary Search
5. Longest Palindromic Substring	Solution	Medium	String
6. ZigZag Conversion	Solution	Medium	String
7. Reverse_Integer	Solution	Medium	Math
8. StringToInteger	Solution	Medium	String
9. Palindrome Number	Solution	Easy	Math
10. Regular Expression Matching	Solution	Hard	String / Dynamic Programming / Backtracking
11. Container With Most Water	Solution	Medium	Medium
12. Integer to Roman	Solution	Medium	String
13. Roman to Integer	Solution	Easy	String
14. Longest Common Prefix	Solution	Easy	String
15. 3Sum	Solution	Medium	Array / Two Pointers
16. 3Sum Closest	Solution	Medium	Array / Two Pointers
17. Letter Combinations of a Phone Number	Solution	Medium	Backtracking / String
18. 4Sum	Solution	Medium	Array
19. Remove Nth Node From End of List	Solution	Medium	Linked List / Two Pointers
20. Valid Parentheses	Solution	Easy	Stack
21. Merge Two Sorted Lists	Solution	Easy	Linked List
22. Generate Parentheses	Solution	Medium	String / Backtracking
23. Merge k Sorted Lists	Solution	Hard	Linked List / Heap
25. Reverse Nodes in k-Group	Solution	Hard	Linked List
26. Remove Duplicates from Sorted Array	Solution	Easy	Array / Two Pointers
28. Implement strStr()	Solution	Easy	String
29. Divide Two Integers	Solution	Easy	String
31. Next Permutation	Solution	Medium	Array
32. Longest Valid Parentheses	Solution	Hard
33. Search in Rotated Sorted Array	Solution	Medium	Array / Binary Search
34. Search for a Range	Solution	Medium	Array / Binary Search
35. Search Insert Position	Solution	Easy	Array / Binary Search
36. Valid Sudoku	Solution	Medium	Hash Table
37. Sudoku Solver	Solution	Hard	Hash Table
39. Combination Sum	Solution	Medium	String
41. First Missing Positive	Solution	Hard	Array
42. Trapping Rain Water	Solution	Hard	Array / Two Pointers / Stack
43. Multiply Strings	Solution	Medium	String
44. Wildcard Matching	Solution	Hard	String / Backtracking / Greedy
45. Jump Game II	Solution	Hard	Hard
46. Permutations	Solution	Medium	Backtracking
47. Permutations II	Solution	Medium	Backtracking
48. Rotate Image	Solution	Medium	Matrix
49. Group Anagrams	Solution	Medium	Hash Table / String
50. Pow(x, n)	Solution	Medium	Binary Search
51. N-Queens	Solution	Hard	Binary Search
52. N-Queens II	Solution	Hard	Binary Search
53. Maximum Subarray	Solution	Easy	Dynamic Programming / Array
54. Spiral Matrix	Solution	Medium	Array
55. Jump Game	Solution	Medium	Array / Greedy
56. Merge Intervals	Solution	Medium	Medium
57. Insert Interval	Solution	Hard	Hard
59. Spiral Matrix II	Solution	Medium	Array
60. Permutation Sequence	Solution	Medium	Backtracking / Math
61. Rotate List	Solution	Medium	Linked List / Two Pointers
62. Unique Paths	Solution	Medium	Array / Dynamic Programming
63. Unique Paths II	Solution	Medium	Medium
64. Minimum Path Sum	Solution	Medium	Array / Dynamic Programming
65. Valid Number	Solution	Hard	Array / Dynamic Programming
66. Plus One	Solution	Easy	Array / Math
68. Text Justification	Solution	Hard	String
69. Sqrt(x)	Solution	Easy	Binary Search / Math
70. Climbing Stairs	Solution	Easy	Dynamic Programming
71. Simplify Path	Solution	Medium	Stack / String
72. Edit Distance	Solution	Hard	Stack / String
73. Set Matrix Zeroes	Solution	Medium	Array
74. Search a 2D Matrix	Solution	Medium	Array / Binary Search
75. Sort Colors	Solution	Medium	Array / Two Pointers
76. Minimum Window Substring	Solution	Hard	Hash Table / Two pointers / String
78. Subsets	Solution	Medium	Array / Backtracking
79. Word Search	Solution	Medium	Matrix / Backtracking
80. Remove Duplicates from Sorted Array II	Solution	Medium	Array / Two Pointers
81. Search in Rotated Sorted Array II	Solution	Medium
82. Remove Duplicates from Sorted List II	Solution	Medium	Linked List
83. Remove Duplicates from Sorted List	Solution	Easy	Linked List
84. Largest Rectangle in Histogram	Solution	Hard	Array
85. Maximal Rectangle	Solution	Hard	Array
86. Partition List	Solution	Medium	Linked List
88. Merge Sorted Array	Solution	Easy	Array / Two Pointers
90. Subsets II	Solution	Medium	Array / Backtracking
91. Decode Ways	Solution	Medium	Dynamic Programming / String
92. Reverse Linked List II	Solution	Medium	Linked List
93. Restore IP Addresses	Solution	Medium
94. Binary Tree Inorder Traversal	Solution	Medium	Tree / Stack
95. Unique Binary Search Trees II	Solution	Medium	Tree
96. Unique Binary Search Trees	Solution	Medium	Tree / DFS
97. Interleaving String	Solution	Hard	Tree / DFS
98. Validate Binary Search Tree	Solution	Medium	Tree
100. Same Tree	Solution	Easy	Tree / DFS
101. Symmetric Tree	Solution	Easy	Tree
102. Binary Tree Level Order Traversal	Solution	Medium	Tree / DFS / BFS
103. Binary Tree Zigzag Level Order Traversal	Solution	Medium	Tree / BFS
104. Maximum Depth of Binary Tree	Solution	Easy	Tree
105. Construct Binary Tree from Preorder and Inorder Traversal	Solution	Medium	Array / Tree / DFS
106. Construct Binary Tree from Inorder and Postorder Traversal	Solution	Medium	Linked List / DFS
107. Binary Tree Level Order Traversal II	Solution	Easy	Tree
108. Convert Sorted Array to Binary Search Tree	Solution	Easy	Tree / DFS
109. Convert Sorted List to Binary Search Tree	Solution	Medium	Linked List / DFS
110. Balanced Binary Tree	Solution	Easy	Tree / DFS
111. Minimum Depth of Binary Tree	Solution	Easy	Tree
112. Path Sum	Solution	Easy	Tree / DFS
113. Path Sum II	Solution	Medium	Tree / DFS
114. Flatten Binary Tree to Linked List	Solution	Medium	Tree / DFS
116. Populating Next Right Pointers in Each Node	Solution	Medium	Tree / BFS
117. Populating Next Right Pointers in Each Node II	Solution	Medium	Tree / Level-order Traversal
119. Pascal's Triangle II	Solution	Easy	Array
120. Triangle	Solution	Medium	Array / Dynamic Programming
121. Best Time to Buy and Sell Stock	Solution	Easy	Array / Dynamic Programming
122. Best Time to Buy and Sell Stock II	Solution	Easy	Tree / DFS
123. Best Time to Buy and Sell Stock III	Solution	Hard	Tree / DFS
124. Binary Tree Maximum Path Sum	Solution	Hard	Tree / DFS
125. Valid Palindrome	Solution	Easy	String / Two Pointers
126. Word Ladder II	Solution	Hard	Array / Unoin Find
127. Word Ladder	Solution	Medium	String / BFS
128. Longest Consecutive Sequence	Solution	Hard	Array / Unoin Find
129. Sum Root to Leaf Numbers	Solution	Medium	Tree / DFS / BFS
130. Surrounded Regions	Solution	Medium	DFS / BFS / Union Find
131. Palindrome Partitioning	Solution	Medium	Backtracking
133. Clone Graph	Solution	Medium	Graph / DFS / BFS
136. Single Number	Solution	Easy	Bit Manipulation
137. Single Number II	Solution	Medium	Dynamic Programming
138. Copy List with Random Pointer	Solution	Medium	Hash Table / Linked List
139. Word Break	Solution	Medium	Dynamic Programming
140. Word Break II	Solution	Hard	Dynamic Programming
141. Linked List Cycle	Solution	Easy	Linked List / Two Pointers
142. Linked List Cycle II	Solution	Easy	Linked List / Two Pointers
143. Reorder List	Solution	Medium	Linked List
144. Binary Tree Preorder Traversal	Solution	Medium	Tree / Stack
146. LRU Cache	Solution	Hard	Design
147. Insertion Sort List	Solution	Medium	Stack / Design
148. Sort List	Solution	Medium	Stack / Design
149. Max Points on a Line	Solution	Hard	Stack / Design
150. Evaluate Reverse Polish Notation	Solution	Medium
151. Reverse Words in a String	Solution	Medium	String
152. Maximum Product Subarray	Solution	Medium	String / Two Pointers
153. Find Minimum in Rotated Sorted Array	Solution	Medium	String / Two Pointers
154. Find Minimum in Rotated Sorted Array II	Solution	Hard	String / Two Pointers
155. Min Stack	Solution	Easy	Stack / Design
157. Read N Characters Given Read4	Solution	Easy	String
158. Read N Characters Given Read4 II - Call multiple times	Solution	Hard	String
159. Longest Substring with At Most Two Distinct Characters	Solution	Hard	String / Two Pointers
160. Intersection of Two Linked Lists	Solution	Easy	String
161. One Edit Distance	Solution	Medium	String
162. Find Peak Element	Solution	Medium	Binary Search
163. Missing Ranges	Solution	Medium	Array
165. Compare Version Numbers	Solution	Medium
166. Fraction to Recurring Decimal	Solution	Medium
167. Two Sum II - Input array is sorted	Solution	Easy
169. Majority Element	Solution	Easy	Array
173. Binary Search Tree Iterator	Solution	Medium	Tree / Stack / Design
179. Largest Number	Solution	Medium
186. Reverse Words in a String II	Solution	Easy	String
187. Repeated DNA Sequences	Solution	Medium
188. Best Time to Buy and Sell Stock IV	Solution	Hard
189. Rotate Array	Solution	Easy
198. House Robber	Solution	Easy	Dynamic Programming
199. Binary Tree Right Side View	Solution	Medium
200. Number of Islands	Solution	Medium	BFS / Union Find
201. Bitwise AND of Numbers Range	Solution	Medium
202. Happy Number	Solution	Easy
203. Remove Linked List Elements	Solution	Easy
204. Count Primes	Solution	Easy
205. Isomorphic Strings	Solution	Easy	Hash Table
206. Reverse Linked List	Solution	Easy	Linked List
207. Course Schedule	Solution	Medium	Graph / BFS / Topological Sort
208. Implement Trie (Prefix Tree)	Solution	Medium	Trie / Design
209. Minimum Size Subarray Sum	Solution	Medium	Array / Two Pointers
210. Course Schedule II	Solution	Medium	Graph / BFS / Topological Sort
212. Word Search II	Solution	Hard
213. House Robber II	Solution	Medium
214. Shortest Palindrome	Solution	Medium	String
215. Kth Largest Element in an Array	Solution	Medium	Medium
216. Combination Sum III	Solution	Medium
217. Contains Duplicate	Solution	Easy
218. The Skyline Problem	Solution	Hard
219. Contains Duplicate II	Solution	Easy
220. Contains Duplicate III	Solution	Medium
221. Maximal Square	Solution	Medium	Dynamic Programming / BFS
223. Rectangle Area	Solution	Medium	Math
224. Basic Calculator	Solution	Hard	String / Stack
226. Invert Binary Tree	Solution	Easy	Tree
227. Basic Calculator II	Solution	Medium	String
230. Kth Smallest Element in a BST	Solution	Medium	Tree
231. Power of Two	Solution	Easy	Easy
232. Implement Queue using Stacks	Solution	Easy
233. Number of Digit One	Solution	Hard
234. Palindrome Linked List	Solution	Easy	Linked List / Two Pointers
235. Lowest Common Ancestor of a Binary Search Tree	Solution	Easy	Tree
236. Lowest Common Ancestor of a Binary Tree	Solution	Medium	Tree
237. Delete Node in a Linked List	Solution	Easy
238. Product of Array Except Self	Solution	Medium	Array
239. Sliding Window Maximum	Solution	Hard	Heap
240. Search a 2D Matrix II	Solution	Medium	Binary Search / Divide and Conquer
241. Different Ways to Add Parentheses	Solution	Medium
242. Valid Anagram	Solution	Easy
243. Shortest Word Distance	Solution	Easy
246. Strobogrammatic Number	Solution	Easy	Hash Table / Math
247. Strobogrammatic Number II	Solution	Medium	Math / Recursion
249. Group Shifted Strings	Solution	Medium	String
251. Flatten 2D Vector	Solution	Medium	Design
252. Meeting Rooms	Solution	Easy	Sort
253. Meeting Rooms II	Solution	Medium	Heap / Sort
255. Verify Preorder Sequence in Binary Search Tree	Solution	Medium	Medium
256. Paint House	Solution	Easy
257. Binary Tree Paths	Solution	Easy	Tree / DFS / BFS
259. 3Sum Smaller	Solution	Medium	Array / Two Pointers
261. Graph Valid Tree	Solution	Medium	Graph / BFS / DFS / Union Find
263. Ugly Number	Solution	Easy	Math
264. Ugly Number II	Solution	Medium	Dynamic Programming / Math
265. Paint House II	Solution	Hard
267. Palindrome Permutation II	Solution	Medium	Backtracking
268. Missing Number	Solution	Easy	Array / Bit Manipulation
269. Alien Dictionary	Solution	Hard	Graph / Topological Sort
270. Closest Binary Search Tree Value	Solution	Easy	Tree / Binary Search
271. Encode and Decode Strings	Solution	Medium	String / Design
272. Closest Binary Search Tree Value II	Solution	Medium	Tree / Stack
273. Integer to English Words	Solution	Hard	String
274. H-Index	Solution	Medium	Sort
276. Paint Fence	Solution	Easy	Dynamic Programming
277. Find the Celebrity	Solution	Medium	Array
278. First Bad Version	Solution	Easy	Binary Search
279. Perfect Squares	Solution	Medium	Math / Dynamic Programming
280. Wiggle Sort	Solution	Medium	Array
281. Zigzag Iterator	Solution	Medium	Design
282. Expression Add Operators	Solution	Hard	Divide and Conquer
283. Move Zeroes	Solution	Easy	Array / Two Pointers
284. Peeking Iterator	Solution	Medium	Design
285. Inorder Successor in BST	Solution	Medium	Tree
286. Walls and Gates	Solution	Medium	BFS
287. Find the Duplicate Number	Solution	Medium
288. Unique Word Abbreviation	Solution	Medium
289. Game of Life	Solution	Medium	Array
290. Word Pattern	Solution	Easy	Hash Table
291. Word Pattern II	Solution	Hard
293. Flip Game	Solution	Easy	String
295. Find Median from Data Stream	Solution	Hard	Heap / Design
296. Best Meeting Point	Solution	Hard
297. Serialize and Deserialize Binary Tree	Solution	Hard	Tree / Design
298. Binary Tree Longest Consecutive Sequence	Solution	Medium	Tree
299. Bulls and Cows	Solution	Medium
300. Longest Increasing Subsequence	Solution	Medium	Binary Search / Dynamic Programming
301. Remove Invalid Parentheses	Solution	Hard	Backtracking / DFS / BFS
303. Range Sum Query - Immutable	Solution	Easy	Dynamic Programming
304. Range Sum Query 2D - Immutable	Solution	Medium	Dynamic Programming
305. Number of Islands II	Solution	Hard	Union Find
307. Range Sum Query - Mutable	Solution	Medium	Segment Tree
308. Range Sum Query 2D - Mutable	Solution	Hard
309. Best Time to Buy and Sell Stock with Cooldown	Solution	Medium	Dynamic Programming
310. Minimum Height Trees	Solution	Medium	BFS/ Graph
311. Sparse Matrix Multiplication	Solution	Medium	Matrix
312. Burst Balloons	Solution	Hard
313. Super Ugly Number	Solution	Medium	Dynamic Programming / Math
314. Binary Tree Vertical Order Traversal	Solution	Medium	BFS
315. Count of Smaller Numbers After Self	Solution	Hard	Divide and Conqur / Binary Search Tree
317. Shortest Distance from All Buildings	Solution	Hard	BFS
318. Maximum Product of Word Lengths	Solution	Medium	Bit Manipulation
320. Generalized Abbreviation	Solution	Medium
322. Coin Change	Solution	Medium
323. Number of Connected Components in an Undirected Graph	Solution	Medium	Graph / Union Find / BFS / DFS
324. Wiggle Sort II	Solution	Medium
325. Maximum Size Subarray Sum Equals k	Solution	Medium	Array / Hash Table
327. Count of Range Sum	Solution	Hard
328. Odd Even Linked List	Solution	Medium
332. Reconstruct Itinerary	Solution	Medium	Graph / DFS
333. Largest BST Subtree	Solution	Medium	Tree
334. Increasing Triplet Subsequence	Solution	Medium	Array
336. Palindrome Pairs	Solution	Hard	Hash Table / String / Trie
337. House Robber III	Solution	Medium
338. Counting Bits	Solution	Medium
339. Nested List Weight Sum	Solution	Easy	DFS
340. Longest Substring with At Most K Distinct Characters	Solution	Hard	Hash Table / String
343. Integer Break	Solution	Medium
344. Reverse String	Solution	Easy	String
345. Reverse Vowels of a String	Solution	Easy
346. Moving Average from Data Stream	Solution	Easy
347. Top K Frequent Elements	Solution	Medium	Hash Table / Heap
348. Design Tic-Tac-Toe	Solution	Medium	Design
349. Intersection of Two Arrays	Solution	Easy
350. Intersection of Two Arrays II	Solution	Easy
351. Android Unlock Patterns	Solution	Medium	DFS / Dynamic Programming
352. Data Stream as Disjoint Intervals	Solution	Hard
353. Design Snake Game	Solution	Medium
354. Russian Doll Envelopes	Solution	Hard	Binary Search / Dynamic Programming
355. Design Twitter	Solution	Medium	Hash Table / Design
357. Count Numbers with Unique Digits	Solution	Medium
358. Rearrange String k Distance Apart	Solution	Hard
359. Logger Rate Limiter	Solution	Easy	Hash Table / Design
360. Sort Transformed Array	Solution	Medium	Math / Two Pointers
361. Bomb Enemy	Solution	Medium	Dynamic Programming
362. Design Hit Counter	Solution	Medium	Design
363. Max Sum of Rectangle No Larger Than K	Solution	Hard
365. Water and Jug Problem	Solution	Medium
368. Largest Divisible Subset	Solution	Medium
369. Plus One Linked List	Solution	Medium	Linked List
370. Range Addition	Solution	Medium
373. Find K Pairs with Smallest Sums	Solution	Medium	Heap
375. Guess Number Higher or Lower II	Solution	Medium
377. Combination Sum IV	Solution	Medium	Dynamic Programming
378. Kth Smallest Element in a Sorted Matrix	Solution	Medium	Binary Search / Heap
380. Insert Delete GetRandom O(1)	Solution	Medium	Hash Table / Design
382. Linked List Random Node	Solution	Medium	Reservoir Sampling
383. Ransom Note	Solution	Easy
384. Shuffle an Array	Solution	Medium
386. Lexicographical Numbers	Solution	Medium
387. First Unique Character in a String	Solution	Easy
392. Is Subsequence	Solution	Medium
393. UTF-8 Validation	Solution	Medium
394. Decode String	Solution	Medium	String / DFS
396. Rotate Function	Solution	Medium
399. Evaluate Division	Solution	Medium	Graph
403. Frog Jump	Solution	Hard
405. Convert a Number to Hexadecimal	Solution	Easy
406. Queue Reconstruction by Height	Solution	Medium
407. Trapping Rain Water II	Solution	Medium
408. Valid Word Abbreviation	Solution	Easy	String
409. Longest Palindrome	Solution	Easy	Hash Table
410. Split Array Largest Sum	Solution	Hard
412. Fizz Buzz	Solution	Easy	Array
416. Partition Equal Subset Sum	Solution	Medium	Dynamic Programming
417. Pacific Atlantic Water Flow	Solution	Medium	DFS / BFS
418. Sentence Screen Fitting	Solution	Medium	Dynamic Programming
433. Minimum Genetic Mutation	Solution	Medium	BFS
435. Non-overlapping Intervals	Solution	Medium	Greedy
436. Find Right Interval	Solution	Medium	Array / Binary Search
438. Find All Anagrams in a String	Solution	Easy	Hash Table
441. Arranging Coins	Solution	Easy	Math
444. Sequence Reconstruction	Solution	Medium	Graph / Topological Sort
450. Delete Node in a BST	Solution	Medium	Tree
451. Sort Characters By Frequency	Solution	Medium	Hash Table / Heap
461. Hamming Distance	Solution	Easy	Bit Manipulation
467. Unique Substrings in Wraparound String	Solution	Medium	Dynamic Programming
473. Matchsticks to Square	Solution	Medium	DFS
477. Total Hamming Distance	Solution	Medium	Bit Manipulation
482. License Key Formatting	Solution	Medium	Array
484. Find Permutation	Solution	Medium	Greedy
486. Predict the Winner	Solution	Medium	Dynamic Programming / Minimax
487. Max Consecutive Ones II	Solution	Medium	Two Pointers
489. Robot Room Cleaner	Solution	Hard	DFS
490. The Maze	Solution	Medium	BFS / DFS
494. Target Sum	Solution	Medium	Backtracking
496. Next Greater Element I	Solution	Easy	Stack
498. Diagonal Traverse	Solution	Medium	Matrix
499. The Maze III	Solution	Hard	DFS / BFS