LeetCode Solutions (JS)

This repository contains solutions for LeetCode problems I've solved(using JS), links to official(and clever unofficial) solutions.

Solutions are grouped by Topics(see topics folder).

Feel free to Fork, Clone or Star this repository.

Also, check out my Python Repository, which contains solutions in Python.

Difficulty	Title	Tags	My Solutions	LeetCode Solution	Other cool solutions	Solved on my own?	Date
	1. Two Sum	HashTable, Array				Yes	2018-10-01
	7. Reverse Integer	Reverse, Math, String				Yes	2018-10-02
	9. Palindrome Number	Reverse, Math, Palindrome				Yes	2018-10-02
	13. Roman to Integer	HashTable, Math		-		Yes	2018-10-03
	14. Longest Common Prefix	String				Yes	2018-10-03
	914. X of a Kind in a Deck of cards	GCD, Math, HashTable				No, almost (couldn't figure good GCD formula)	2018-10-07
	2. Add Two Numbers	LinkedList				Yes	2018-10-07
	3. Longest Substring Without Repeating Characters	String, HashTable				Yes, but suboptimal	2018-10-11
	4. Median of Two Sorted Arrays	Array, Median			[YouTube] Median of two sorted arrays - standard solution	Yes, but suboptimal	2018-10-12
	5. Longest Palindromic Substring	String, Palindrome			Manacher's Algorithm (O(N))	Yes	2018-10-13
	6. ZigZag Conversion	String				Yes	2018-10-14
	8. String to Integer (atoi)	String, Number		-		Yes	2018-10-14
	925. Long Pressed Name	String				Yes	2018-10-21
	926. Flip String to Monotone Increasing	Math, String			1) "Sliding" + counting Prefix Sums, 2) Counting while iterating	No, wrongly discarded thought to try all possible solutions	2018-10-23
	771. Jewels and Stones	HashTable		-		Yes	2018-11-19
	933. Number of Recent Calls	Array, Queue				Yes, but subopt., it's better to use Queue	2018-11-20
	937. Reoder Log Files	String				Yes	2018-11-24
	938. Range Sum of BST	Tree, BST				Yes	2018-11-24
	941. Valid Mountain Array	Array				Yes	2018-11-24
	944. Delete Columns to Make Sorted	Array				Yes	2018-11-24
	945. Minimum Increment to Make Array Unique	Array				Yes, but there is faster solution (see Sol. 1)	2018-12-06
	946. Validate Stack Sequences	Stack, Simulation				No, didn't get how to simulate the process	2018-12-07
	949. Largest Time for Given Digits	Array, Permu- tations			1) Generating permut-s in descending order, 2) Using 3 for loops instead of permut-s, 3) Interesting idea with limits in separate array	Yes, but with hardcoded permut-s	2018-12-08
	950. Reveal Cards In Increasing Order	Stack, Simulation				Almost, still didn't figure how to simulate the process	2018-12-10
	951. Flip Equivalent Binary Trees	Tree				Yes	2018-12-12
	226. Invert Binary Tree	Tree				Yes	2018-12-13
	953. Verifying an Alien Dictionary	HashTable				Yes	2018-12-15
	954. Array of Doubled Pairs	HashTable				Yes	2018-12-15
	955. Delete Columns to Make Sorted II	HashTable				Yes	2018-12-15
	20. Valid Parentheses	Stack, String, HashTable				Yes	2019-08-15
	26. Remove Duplicates from Sorted Array	Array				Yes	2019-08-15
	27. Remove Element	Array, Two Pointers				Yes	2019-08-15
	28. Implement strStr()	String, Search, Rabin-Karp, KMP		-		KMP, Rabin-Karp	2019-08-20
	453. Minimum Moves to Equal Array Elements	Array, Math		-		Yes	2019-08-21
	342. Power of Four	Bitwise		-		Bitwise and radix 4	2019-08-21
	326. Power of Three	Bitwise			1) List of several solutions	Bitwise, radix of 3	2019-08-21
	557. Reverse Words in a String III	String				Yes	2019-08-21
	434. Number of Segments in a String	String, Regex				Yes	2019-08-21
	1052. Grumpy Bookstore Owner	Array, Sliding Window		-	1) Good example of not calculating initial window sum	Sliding Window - w/o initial calculation	2019-08-21
	238. Product of Array Except Self	Array, Prefix Product, Suffix Product				Prefix Product, Suffix Product	2019-08-22
	746. Min Cost Climbing Stairs	DP, Sliding min Sum, Recursion			1) Changing array in place	Interesting sliding min sum, recursion	2019-08-22
	70. Climbing Stairs	DP, Sliding Sum, Recursion				Sliding Sum, DP	2019-08-22
	559. Maximum Depth of N-ary Tree	Tree, BFS, DFS, Queue		-	1) Using single queue for BFS	DFS with single queue	2019-08-22
	104. Maximum Depth of Binary Tree	Tree, BFS, DFS, Queue		-	1) Shoft recursive DFS	Shoft DFS, BFS with single queue	2019-08-22
	278. First Bad Version	Array, Binary Search				Binary search(no overflow), w/o additional var	2019-08-23
	38. Count and Say	String		-	1) Commenters discuss Runtime Complexity	Yes	2019-08-27
	35. Search Insert Position	Array, Binary Search		-	1) Simply return low at the end	Array Binary Search	2019-08-28
	203. Remove Linked List Elements	LinkedList		-	1) Short recursive solution, 2) Short iterative without dummy head, 3) Iterative with Dummy head	Dummy head, Recursive, Iterative	2019-08-28
	141. Linked List Cycle	LinkedList, Tortoise and Hare				Tortoise and Hare	2019-08-29
	206. Reverse Linked List	LinkedList, Reverse				Iterative, Recursive	2019-08-29
	83. Remove Duplicates from Sorted List	LinkedList				Hanlde memory leak	2019-08-29
	160. Intersection of Two Linked Lists	LinkedList, Two pointers				1. Compare lengths. 2. Go till the end, then start from other list.	2019-08-29
	67. Add Binary	Math, Binary		-		Binary	2019-08-29
	171. Excel Sheet Column Number	Math, Base 26		-		Base 26 to Base 10	2019-08-29
	728. Self Dividing Numbers	Math				Brute-force is the only way	2019-08-29
	485. Max Consecutive Ones	Array		-		Simple counting	2019-08-29
	997. Find the Town Judge	Graph		-		Graph	2019-08-29
	543. Diameter of Binary Tree	Tree, DFS, BFS			1) Iterative BFS solution	Height is not Depth (see comments in off. solution)	2019-08-30
	136. Single Number	Bitwise, XOR, Math				XOR	2019-08-30
	101. Symmetric Tree	Tree, DFS, BFS, Queue				BFS - extracting 2 elements from the queue	2019-08-30
	121. Best Time to Buy and Sell Stock	Array, DP (kind of), Rolling				DP with O(1) space, rolling min	2019-08-30
	66. Plus One	Math		-		Can be done without carry	2019-08-30
	581. Shortest Unsorted Continuous Subarray	Array, Stack, Peaks and Falls			1) Short 1 loop solution (more readable 2 loops in the comments)	Stack, Rolling min/max, Tricky	2019-09-03
	169. Majority Element	Array, HashTable, Divide and Conquer, Bitwise, Boyer-Moore Voting Algorithm			1) Bit manipulation solution	Divide and Conquer, Boyer-Moore Voting Algorithm, Bitwise majority mask, Sorting trick	2019-09-03
	198. House Robber	DP		-	1) Recursive, with Memo, DP with array, DP with vars	DP, many ways of starting and ending iteraction, vars only	2019-09-03
	412. Fizz Buzz	String				Divisible by 3 and 5 is divisible by 15 (prime numbers)	2019-09-04
	437. Path Sum III	Tree, Prefix Sum, DFS, Paths Sums		-	1) Most optimal solution with Prefix Sums, 2) Good Space/Runtime estimations explanations, 3) Very suboptimal solution, beware	Prefix Sums for paths sums in Tree, while DFS-ing	2019-09-04
	1171. Remove Zero Sum Consecutive Nodes from Linked List	LinkedList, Prefix Sums, HashTable, Removal		-	1) Solution using HashTable, 2) Good illustration	1. Prefix Sums + HashTable in Linked List 2. Removal in Linked List	2019-09-04
	88. Merge Sorted Array	Array		-		Simple 3 pointers	2019-09-05
	268. Missing Number	Math, Binary Search, Bitwise XOR, Arithmetic Progr.			1) Interesting Binary Search idea (suboptimal)	1. Arithmetic progr., 2. Bitwise XOR, 3. Binary Search	2019-09-05
	237. Delete Node in a Linked List	LinkedList				Brain teaser - copy value to the left instead of removing	2019-09-05
	94. Binary Tree Inorder Traversal	Tree, BFS with Stack, BFS, Morris Traversal				1. BFS with Stack, 2. DFS, 3. Morris Traversal	2019-09-06
	387. First Unique Character in a String	String, HashTable				Iterate 2nd time over HashTable or original string	2019-09-06
	118. Pascal's Triangle	DP				Simple DP	2019-09-06
	680. Valid Palindrome II	String, Palindrome				Palindrome (not scrambled)	2019-09-09
	1122. Relative Sort Array	Array, Sorting, HashTable, Count Array		-	1) L1 log(L1) + L2 sorting solution, 2) Helper count array	1. Helper count array, 2. Sorting by key from HashTable	2019-09-09
	108. Convert Sorted Array to Binary Search Tree	Tree, BST, Binary Search		-	1) Iterative solution with 3 stacks	BST combined with tree generation, interesting iterative solution	2019-09-09
	172. Factorial Trailing Zeroes	Math, Factors, divisors		-	1) Good explanation - why looking for 5 works	Interesting brainstorm math, factors	2019-09-10
	189. Rotate Array	Array, Shift, swap, pop, push				Many ways to solve: reverse, jump and swap, slice, pop and push	2019-09-10
	350. Intersection of Two Arrays II	Array, Intersect.		-		Simple HashTable	2019-09-10
	560. Subarray Sum Equals K	Array, HashTable, Rolling Sums, Math			1) Why 2 pointers won't work in this case (negative numbers)	HashTable with Rolling Sums, tricky idea to get number of rolling sums	2019-09-11
	190. Reverse Bits	Bitwise, Binary		-	1) Good JS explanation, "res >>> 0" at the end.	Logical >>> and Arithmetic >> shifts, Bitwise operations	2019-09-11
	122. Best Time to Buy and Sell Stock II	Array, Peak and Valleys				Interesting "Next Peak and Valley" approach	2019-09-11
	53. Maximum Subarray	Array, DP, Recrursion, Memo, Rolling Sum		-		Rolling Sum, DP, Recursion, Memo	2019-09-12
	152. Maximum Product Subarray	Array, Rolling Products		-	1) Swap min and max, 2) Iterate left to right and right to left	Rolling min/max products, min/max swap	2019-09-12
	110. Balanced Binary Tree	Tree, BFS, DFS		-	1) (!) Tricky Iterative BFS, 2) Suboptimal DFS, 2 different funcs	(!) Tricky Iterative BFS, DFS with return -1 or res obj	2019-09-14
	263. Ugly Number	Math, Prime factors		-	1) Good use of JS "for of" loop to iterate over array [2, 3, 5]	Getting Prime Factors	2019-09-16
	1160. Find Words That Can Be Formed by Characters	String, HashTable		-		Simple HashTable and counting	2019-09-17
	134. Gas Station	Array, Brain Teaser, Tricky			1) Answer proof	Very tricky, Brain Teaser	2019-09-17
	704. Binary Search	Array, Binary Search				Simple binary search, 2 ways to solve using different Invariants	2019-09-17
	153. Find Minimum in Rotated Sorted Array	Array, Binary Search				Interesting Invariants in Binary Search	2019-09-17
	345. Reverse Vowels of a String	String, Two Pointers, Stack		-		Two pointers or less optimal trick with Stack	2019-09-17
	292. Nim Game	Math, Brain Teaser				Brain Teaser	2019-09-17
	589. N-ary Tree Preorder Traversal	Tree, DFS, Iterative DFS				Iterative DFS	2019-09-18
	112. Path Sum	Tree, DFS, Iterative, Recursive, Stack				Iterative traversals using stack	2019-09-19
	530. Minimum Absolute Difference in BST	Tree, In-order Traversal		-	1) Iterative In-order Traversal in BT	Iterative In-order Traversal	2019-09-19
	744. Find Smallest Letter Greater Than Target	String, Binary Search				Simple Binary Search	2019-09-19
	107. Binary Tree Level Order Traversal II	Tree, Iterative BFS, Recursive DFS		-		Recursive DFS passing level, to make BFS-like processing	2019-09-19
	102. Binary Tree Level Order Traversal	Tree, Iterative BFS, Recursive DFS				Recursive DFS passing level, to make BFS-like processing	2019-09-19
	709. To Lower Case	String, RegExp		-		Simple RegExp or char from/to code	2019-09-20
	119. Pascal's Triangle II	Math, DP		-	1) Math formula for specific row/cell in Pascal's triangle	1. Iterating back, not to store the previous original value 2. Pascal's Triangle Math Formula	2019-09-21
	669. Trim a Binary Search Tree	Tree, BST, Deleting, DFS, Recursive, Iterative			1) Iterative solution	Deleting nodes inbetween, interesting Recursive and Iterative solutions	2019-09-23
	836. Rectangle Overlap	Math, Geometry, Rect, Intersect., Area				Check if it's outside or find intersection area (square)	2019-09-23
	111. Minimum Depth of Binary Tree	Tree, Iterative BFS, Iterative DFS, Recursive DFS				Iterative DFS, BFS is more efficient for this problem	2019-09-24
	33. Search in Rotated Sorted Array	Array, Binary Search				Find min in rotated array, then binary or combined 1 pass	2019-09-24
	716. Max Stack	Stack, TreeMap, Doubly Linked List				1. Additional Max Stack 2. Interesting Doubly Linked List + TreeMap official solution	2019-09-25
	875. Koko Eating Bananas	Array, Binary Search, Trial and Error				Trial and Error using Binary Search	2019-09-25
	811. Subdomain Visit Count	HashTable, String, Substring				.indexOf is better than .split	2019-09-25
	1110. Delete Nodes And Return Forest	Tree, DFS, Disjoint, Delete, Subtree		-	1) Good explanation about passing info from parent to child and vice versa	Communic. between child and parent to make code more concise	2019-09-26
	221. Maximal Square	DP, Matrix			1) Good optimizing process, using vector instead of sinle row	"2D" DP in matrix	2019-09-26
	346. Moving Average from Data Stream	Queue, Array, Linked List		-		Queue using Array or LinkedList	2019-09-28
	204. Count Primes	Math, Primes, Sieve of Eratos.		-	1) Clean Sieve of Eratos. solution, 2) Sieve of Eratos. explained	Primes, Sieve of Eratos.	2019-09-30
	538. Convert BST to Greater Tree	Tree, BST, Reverse Morris In-Order Traversal, DFS				Reverse DFS Traversal, Iterative, Recursive with sharedObj and parameters	2019-09-30
	819. Most Common Word	String, RegEx, HashTable				RegEx (split by "inverted" RegEx), simple HashTable count	2019-09-30
	293. Flip Game	String, Substring		-	1) .indexOf in for loop - interesting idea	Simple substring problem	2019-09-30
	383. Ransom Note	HashTable, Chars array counter		-		Prefix decrement in if for array item	2019-10-01
	461. Hamming Distance	Bitwise, Brian Kernighan bit counting, XOR		-	1) XOR and Brian Kernighan's bit counting	XOR, Brian Kernighan's bit counting	2019-10-01
	243. Shortest Word Distance	Array, Min Dist				Simple min dist	2019-10-01
	1119. Remove Vowels from a String	String, RegEx		-		Replace RegEx or HashSet	2019-10-02
	616. Add Bold Tag in String	Intervals, Intervals Merge, String, Substring, Mask, indexOf, ``				1. String mask, 2. trick "while ((i = indexOf(...)) >= 0)", 3. Merging intervals	2019-10-03
	15. 3Sum	Array, Sorting, Two Pointers, HashTable		-	1) Sorting, two pointers solution explained	Sorting -> two pointers, a lot of tricks to stop/break earlier and skip	2019-10-03
	11. Container With Most Water	Array, Two Pointers				Interesting Two Pointers application	2019-10-03
	371. Sum of Two Integers	Bitwise, Addition		-	1) A lot of Bitwise techniques	Addition using &, ^, <<	2019-10-04
	908. Smallest Range I	Array, Math				Simple math, slightly confusing question	2019-10-04
	1215. Stepping Numbers	Tree, Digits, BFS, Queue		-		Iterative BFS - sorting isn't needed (in contrast to DFS)	2019-10-07
	883. Projection Area of 3D Shapes	Array, 3D, Projection				Trick with swapping r, c, since matrix is NxN	2019-10-08
	338. Counting Bits	Bitwise, DP, Least signif. bit, Most signif. bit				DP and bitwise, bits rules	2019-10-10
	276. Paint Fence	DP, Probability, Math		-	1) Decent explanation	Probability, DP	2019-10-16
	496. Next Greater Element I	Stack, Monotonic Stack				Monotonic Stack	2019-10-17
	1232. Check If It Is a Straight Line	Geometry, Math		-	1) Check Slopes, 2) Is Triangle area == 0	Formulas: Slopes, Triangle area	2019-10-21
	1233. Remove Sub-Folders from the Filesystem	String, Substring, HashSet, Sorting		-	1) 1. Sort by length -> use HashSet 2. Sort lexic. -> compare only with previous potential parent	Difficult time/space estim., interesting solutions	2019-10-22
	232. Implement Queue using Stacks	Stack, Queue				2 Stacks(1 reversed) to get amortized O(1) pop	2019-10-22
	674. Longest Continuous Increasing Subseq.	Array, Subseq.		-		Anchor technique, Sliding Window	2019-10-22
	120. Triangle	DP, Bottom-Up DP		-	1) Bottom-up explanation	DP Bottom-Up, In-place	2019-10-24
	1022. Sum of Root To Leaf Binary Numbers	Tree, Recursive, Iterative, Stack		-		Stack with Tuple or 2 values, Iterative DFS	2019-10-24
	129. Sum Root to Leaf Numbers	Tree, Recursive, Iterative, Stack		-		Same as #1022	2019-10-24
	124. Binary Tree Maximum Path Sum	Tree, Recursive, Path				Max gain idea: left_sum = max (left_sum, 0), to shorten code	2019-10-25
	1171. Remove Zero Sum Consecutive Nodes from Linked List	LinkedList, HashTable, Prefix, Sum, Delete		-	1) Smart two-pass solution (last), 2) Explanation picture	No memory leak in GC, smart two pass	2019-10-29
	733. Flood Fill	Matrix, DFS, BFS, Iterative, Recursive				Good template for DFS, BFS problems	2019-10-29
	443. String Compress.	String, Two Pointers		-		Iterate and check the next to handle last char, Iterate over digits without split	2019-10-29
	138. Copy List with Random Pointer	LinkedList, HashTable, Recursive			1) Great one pass, two pass code, 2) O(1) official solution explained	No need for new List, store nodes only in Map.	2019-10-31
	594. Longest Harmonious Subseq.	Array, HashTable, Sorting				Tricky iteration after Sorting	2019-11-04
	548. Split Array with Equal Sum	Array, HashTable, Prefix Sum				Prefix sums, HashTable, Skip recalc. Zeros	2019-11-06