Leetcode

Now start to work on leetcode for fun.

Using ruby to start because ruby looks like a elegant language.

I have solved 97 / 645 problems while 120 problems are still locked.

Good reference

• Algorithms Notes | 演算法笔记 (Chinese)

  http://www.csie.ntnu.edu.tw/~u91029/index.html

repository for reference

leetcode-ruby leetcode

mostly in javascript:

LeetCode-Solutions

in go:

Leetcode-go

Chart

This part is generated by generator.js

Leetcode Solutions chart generated with JavaScript

Update time: Sun Apr 01 2018 18:04:37 GMT+0800 (CST)

I have solved 104 / 726 problems while 133 problems are still locked.

(Notes: 📘 means you need to buy a book from Leetcode)

#	Title	Source Code	Explanation	Difficulty
829	Subdomain Visit Count			Easy
828	Chalkboard XOR Game			Hard
827	Expressive Words			Medium
826	Soup Servings			Medium
825	Max Increase to Keep City Skyline			Medium
824	Number of Lines To Write String			Easy
823	Split Array With Same Average			Hard
822	Unique Morse Code Words			Easy
821	Bricks Falling When Hit			Hard
820	Find Eventual Safe States			Medium
819	Minimum Swaps To Make Sequences Increasing			Medium
818	Similar RGB Color 📘			Easy
815	Champagne Tower			Medium
814	Smallest Rotation with Highest Score			Hard
813	All Paths From Source to Target			Medium
812	Rotate String			Easy
811	Number of Subarrays with Bounded Maximum			Medium
810	Valid Tic-Tac-Toe State			Medium
809	Preimage Size of Factorial Zeroes Function			Hard
808	Number of Matching Subsequences			Medium
807	Custom Sort String			Medium
806	Domino and Tromino Tiling			Medium
805	Escape The Ghosts			Medium
804	Rotated Digits			Easy
803	Cheapest Flights Within K Stops			Medium
802	K-th Smallest Prime Fraction			Hard
801	Is Graph Bipartite?			Medium
800	Letter Case Permutation			Easy
799	Minimum Distance Between BST Nodes			Easy
798	Transform to Chessboard			Hard
797	Rabbits in Forest			Medium
796	Reaching Points			Hard
795	K-th Symbol in Grammar			Medium
794	Swim in Rising Water			Hard
793	Swap Adjacent in LR String			Medium
791	Split BST 📘			Medium
790	Global and Local Inversions			Medium
788	Minimize Max Distance to Gas Station 📘			Hard
787	Sliding Puzzle			Hard
785	Basic Calculator III 📘			Hard
782	Jewels and Stones			Easy
781	Basic Calculator IV			Hard
780	Max Chunks To Make Sorted			Medium
779	Max Chunks To Make Sorted II			Hard
778	Reorganize String			Medium
777	Toeplitz Matrix			Easy
770	Couples Holding Hands			Hard
769	Largest Plus Sign			Medium
768	Partition Labels			Medium
767	Prime Number of Set Bits in Binary Representation			Easy
763	Special Binary String			Hard
762	Find Anagram Mappings 📘			Easy
761	Employee Free Time 📘			Hard
760	Bold Words in String 📘			Easy
759	Set Intersection Size At Least Two			Hard
757	Pyramid Transition Matrix			Medium
756	Pour Water 📘			Medium
755	Reach a Number			Medium
754	Cracking the Safe			Hard
753	Open the Lock			Medium
752	IP to CIDR 📘			Easy
751	Number Of Corner Rectangles 📘			Medium
750	Contain Virus			Hard
749	Shortest Completing Word			Medium
748	Largest Number At Least Twice of Others			Easy
747	Min Cost Climbing Stairs			Easy
746	Prefix and Suffix Search			Hard
745	Find Smallest Letter Greater Than Target			Easy
744	Network Delay Time			Medium
743	Closest Leaf in a Binary Tree 📘			Medium
741	Cherry Pickup			Hard
740	Delete and Earn			Medium
739	Daily Temperatures			Medium
738	Monotone Increasing Digits			Medium
737	Sentence Similarity II 📘			Medium
736	Parse Lisp Expression			Hard
735	Asteroid Collision			Medium
734	Sentence Similarity 📘			Easy
733	Flood Fill			Easy
732	My Calendar III			Hard
731	My Calendar II			Medium
730	Count Different Palindromic Subsequences			Hard
729	My Calendar I			Medium
728	Self Dividing Numbers			Easy
727	Minimum Window Subsequence 📘			Hard
726	Number of Atoms			Hard
725	Split Linked List in Parts			Medium
724	Find Pivot Index			Easy
723	Candy Crush 📘			Medium
722	Remove Comments			Medium
721	Accounts Merge			Medium
720	Longest Word in Dictionary	javascript		Easy
719	Find K-th Smallest Pair Distance			Hard
718	Maximum Length of Repeated Subarray			Medium
717	1-bit and 2-bit Characters			Easy
716	Max Stack 📘			Hard
715	Range Module			Hard
714	Best Time to Buy and Sell Stock with Transaction Fee			Medium
713	Subarray Product Less Than K			Medium
712	Minimum ASCII Delete Sum for Two Strings			Medium
711	Number of Distinct Islands II 📘			Hard
699	Falling Squares			Hard
698	Partition to K Equal Sum Subsets			Medium
697	Degree of an Array			Easy
696	Count Binary Substrings			Easy
695	Max Area of Island			Easy
694	Number of Distinct Islands 📘			Medium
693	Binary Number with Alternating Bits			Easy
692	Top K Frequent Words			Medium
691	Stickers to Spell Word			Hard
690	Employee Importance			Easy
689	Maximum Sum of 3 Non-Overlapping Subarrays			Hard
688	Knight Probability in Chessboard			Medium
687	Longest Univalue Path			Easy
686	Repeated String Match			Easy
685	Redundant Connection II			Hard
684	Redundant Connection			Medium
683	K Empty Slots 📘			Hard
682	Baseball Game			Easy
681	Next Closest Time 📘			Medium
680	Valid Palindrome II			Easy
679	24 Game			Hard
678	Valid Parenthesis String			Medium
677	Map Sum Pairs			Medium
676	Implement Magic Dictionary			Medium
675	Cut Off Trees for Golf Event			Hard
674	Longest Continuous Increasing Subsequence			Easy
673	Number of Longest Increasing Subsequence			Medium
672	Bulb Switcher II			Medium
671	Second Minimum Node In a Binary Tree			Easy
670	Maximum Swap			Medium
669	Trim a Binary Search Tree			Easy
668	Kth Smallest Number in Multiplication Table			Hard
667	Beautiful Arrangement II			Medium
666	Path Sum IV 📘			Medium
665	Non-decreasing Array			Easy
664	Strange Printer			Hard
663	Equal Tree Partition 📘			Medium
662	Maximum Width of Binary Tree			Medium
661	Image Smoother			Easy
660	Remove 9 📘			Hard
659	Split Array into Consecutive Subsequences			Medium
658	Find K Closest Elements			Medium
657	Judge Route Circle			Easy
656	Coin Path 📘			Hard
655	Print Binary Tree			Medium
654	Maximum Binary Tree			Medium
653	Two Sum IV - Input is a BST			Easy
652	Find Duplicate Subtrees			Medium
651	4 Keys Keyboard 📘			Medium
650	2 Keys Keyboard			Medium
649	Dota2 Senate			Medium
648	Replace Words			Medium
647	Palindromic Substrings	ruby		Medium
646	Maximum Length of Pair Chain			Medium
645	Set Mismatch			Easy
644	Maximum Average Subarray II 📘			Hard
643	Maximum Average Subarray I			Easy
642	Design Search Autocomplete System 📘			Hard
640	Solve the Equation			Medium
639	Decode Ways II			Hard
638	Shopping Offers			Medium
637	Average of Levels in Binary Tree			Easy
636	Exclusive Time of Functions			Medium
635	Design Log Storage System 📘			Medium
634	Find the Derangement of An Array 📘			Medium
633	Sum of Square Numbers			Easy
632	Smallest Range			Hard
631	Design Excel Sum Formula 📘			Hard
630	Course Schedule III			Hard
629	K Inverse Pairs Array			Hard
628	Maximum Product of Three Numbers			Easy
625	Minimum Factorization 📘			Medium
624	Maximum Distance in Arrays 📘			Easy
623	Add One Row to Tree	javascript		Medium
621	Task Scheduler			Medium
617	Merge Two Binary Trees			Easy
616	Add Bold Tag in String 📘			Medium
611	Valid Triangle Number	ruby		Medium
609	Find Duplicate File in System			Medium
606	Construct String from Binary Tree	ruby		Easy
605	Can Place Flowers			Easy
604	Design Compressed String Iterator 📘			Easy
600	Non-negative Integers without Consecutive Ones			Hard
599	Minimum Index Sum of Two Lists	go		Easy
598	Range Addition II	ruby		Easy
594	Longest Harmonious Subsequence			Easy
593	Valid Square			Medium
592	Fraction Addition and Subtraction			Medium
591	Tag Validator			Hard
588	Design In-Memory File System 📘			Hard
587	Erect the Fence			Hard
583	Delete Operation for Two Strings			Medium
582	Kill Process 📘			Medium
581	Shortest Unsorted Continuous Subarray			Easy
576	Out of Boundary Paths			Medium
575	Distribute Candies			Easy
573	Squirrel Simulation 📘			Medium
572	Subtree of Another Tree			Easy
568	Maximum Vacation Days 📘			Hard
567	Permutation in String			Medium
566	Reshape the Matrix			Easy
565	Array Nesting			Medium
564	Find the Closest Palindrome			Hard
563	Binary Tree Tilt			Easy
562	Longest Line of Consecutive One in Matrix 📘			Medium
561	Array Partition I			Easy
560	Subarray Sum Equals K	ruby		Medium
557	Reverse Words in a String III			Easy
556	Next Greater Element III	ruby		Medium
555	Split Concatenated Strings 📘			Medium
554	Brick Wall	ruby		Medium
553	Optimal Division			Medium
552	Student Attendance Record II			Hard
551	Student Attendance Record I			Easy
549	Binary Tree Longest Consecutive Sequence II 📘			Medium
548	Split Array with Equal Sum 📘			Medium
547	Friend Circles			Medium
546	Remove Boxes			Hard
545	Boundary of Binary Tree 📘			Medium
544	Output Contest Matches 📘			Medium
543	Diameter of Binary Tree			Easy
542	01 Matrix	ruby		Medium
541	Reverse String II			Easy
540	Single Element in a Sorted Array	ruby		Medium
539	Minimum Time Difference			Medium
538	Convert BST to Greater Tree			Easy
537	Complex Number Multiplication			Medium
536	Construct Binary Tree from String 📘			Medium
535	Encode and Decode TinyURL			Medium
533	Lonely Pixel II 📘			Medium
532	K-diff Pairs in an Array			Easy
531	Lonely Pixel I 📘			Medium
530	Minimum Absolute Difference in BST			Easy
529	Minesweeper			Medium
527	Word Abbreviation 📘			Hard
526	Beautiful Arrangement			Medium
525	Contiguous Array			Medium
524	Longest Word in Dictionary through Deleting			Medium
523	Continuous Subarray Sum			Medium
522	Longest Uncommon Subsequence II			Medium
521	Longest Uncommon Subsequence I			Easy
520	Detect Capital	javascript go		Easy
517	Super Washing Machines			Hard
516	Longest Palindromic Subsequence			Medium
515	Find Largest Value in Each Tree Row			Medium
514	Freedom Trail			Hard
513	Find Bottom Left Tree Value	ruby		Medium
508	Most Frequent Subtree Sum			Medium
507	Perfect Number			Easy
506	Relative Ranks			Easy
505	The Maze II 📘			Medium
504	Base 7			Easy
503	Next Greater Element II	ruby		Medium
502	IPO			Hard
501	Find Mode in Binary Search Tree			Easy
500	Keyboard Row			Easy
499	The Maze III 📘			Hard
498	Diagonal Traverse			Medium
496	Next Greater Element I			Easy
495	Teemo Attacking			Medium
494	Target Sum			Medium
493	Reverse Pairs			Hard
492	Construct the Rectangle	ruby		Easy
491	Increasing Subsequences			Medium
490	The Maze 📘			Medium
488	Zuma Game			Hard
487	Max Consecutive Ones II 📘			Medium
486	Predict the Winner			Medium
485	Max Consecutive Ones	javascript		Easy
484	Find Permutation 📘			Medium
483	Smallest Good Base	ruby		Hard
482	License Key Formatting			Easy
481	Magical String			Medium
480	Sliding Window Median			Hard
479	Largest Palindrome Product			Easy
477	Total Hamming Distance			Medium
476	Number Complement			Easy
475	Heaters			Easy
474	Ones and Zeroes			Medium
473	Matchsticks to Square			Medium
472	Concatenated Words			Hard
471	Encode String with Shortest Length 📘			Hard
469	Convex Polygon 📘			Medium
468	Validate IP Address			Medium
467	Unique Substrings in Wraparound String			Medium
466	Count The Repetitions			Hard
465	Optimal Account Balancing 📘			Hard
464	Can I Win			Medium
463	Island Perimeter			Easy
462	Minimum Moves to Equal Array Elements II			Medium
461	Hamming Distance			Easy
460	LFU Cache			Hard
459	Repeated Substring Pattern			Easy
456	132 Pattern			Medium
455	Assign Cookies			Easy
454	4Sum II			Medium
453	Minimum Moves to Equal Array Elements			Easy
452	Minimum Number of Arrows to Burst Balloons			Medium
451	Sort Characters By Frequency	ruby		Medium
450	Delete Node in a BST	ruby		Medium
449	Serialize and Deserialize BST	ruby		Medium
448	Find All Numbers Disappeared in an Array			Easy
447	Number of Boomerangs			Easy
446	Arithmetic Slices II - Subsequence			Hard
445	Add Two Numbers II	ruby		Medium
444	Sequence Reconstruction 📘			Medium
443	String Compression			Easy
442	Find All Duplicates in an Array	ruby		Medium
441	Arranging Coins			Easy
440	K-th Smallest in Lexicographical Order			Hard
439	Ternary Expression Parser 📘			Medium
438	Find All Anagrams in a String			Easy
437	Path Sum III	ruby		Easy
436	Find Right Interval			Medium
435	Non-overlapping Intervals			Medium
434	Number of Segments in a String			Easy
432	All O`one Data Structure			Hard
425	Word Squares 📘			Hard
424	Longest Repeating Character Replacement			Medium
423	Reconstruct Original Digits from English			Medium
422	Valid Word Square 📘			Easy
421	Maximum XOR of Two Numbers in an Array			Medium
420	Strong Password Checker			Hard
419	Battleships in a Board			Medium
418	Sentence Screen Fitting 📘			Medium
417	Pacific Atlantic Water Flow			Medium
416	Partition Equal Subset Sum			Medium
415	Add Strings			Easy
414	Third Maximum Number			Easy
413	Arithmetic Slices			Medium
412	Fizz Buzz			Easy
411	Minimum Unique Word Abbreviation 📘			Hard
410	Split Array Largest Sum			Hard
409	Longest Palindrome			Easy
408	Valid Word Abbreviation 📘			Easy
407	Trapping Rain Water II			Hard
406	Queue Reconstruction by Height			Medium
405	Convert a Number to Hexadecimal			Easy
404	Sum of Left Leaves			Easy
403	Frog Jump			Hard
402	Remove K Digits	ruby		Medium
401	Binary Watch	ruby		Easy
400	Nth Digit			Easy
399	Evaluate Division			Medium
398	Random Pick Index			Medium
397	Integer Replacement			Medium
396	Rotate Function			Medium
395	Longest Substring with At Least K Repeating Characters			Medium
394	Decode String	go		Medium
393	UTF-8 Validation			Medium
392	Is Subsequence			Medium
391	Perfect Rectangle			Hard
390	Elimination Game			Medium
389	Find the Difference			Easy
388	Longest Absolute File Path			Medium
387	First Unique Character in a String			Easy
386	Lexicographical Numbers			Medium
385	Mini Parser			Medium
384	Shuffle an Array			Medium
383	Ransom Note			Easy
382	Linked List Random Node			Medium
381	Insert Delete GetRandom O(1) - Duplicates allowed			Hard
380	Insert Delete GetRandom O(1)			Medium
379	Design Phone Directory 📘			Medium
378	Kth Smallest Element in a Sorted Matrix			Medium
377	Combination Sum IV			Medium
376	Wiggle Subsequence			Medium
375	Guess Number Higher or Lower II			Medium
374	Guess Number Higher or Lower			Easy
373	Find K Pairs with Smallest Sums			Medium
372	Super Pow			Medium
371	Sum of Two Integers			Easy
370	Range Addition 📘			Medium
369	Plus One Linked List 📘			Medium
368	Largest Divisible Subset			Medium
367	Valid Perfect Square			Easy
366	Find Leaves of Binary Tree 📘			Medium
365	Water and Jug Problem			Medium
364	Nested List Weight Sum II 📘			Medium
363	Max Sum of Rectangle No Larger Than K			Hard
362	Design Hit Counter 📘			Medium
361	Bomb Enemy 📘			Medium
360	Sort Transformed Array 📘			Medium
359	Logger Rate Limiter 📘			Easy
358	Rearrange String k Distance Apart 📘			Hard
357	Count Numbers with Unique Digits	ruby		Medium
356	Line Reflection 📘			Medium
355	Design Twitter			Medium
354	Russian Doll Envelopes			Hard
353	Design Snake Game 📘			Medium
352	Data Stream as Disjoint Intervals			Hard
351	Android Unlock Patterns 📘			Medium
350	Intersection of Two Arrays II			Easy
349	Intersection of Two Arrays			Easy
348	Design Tic-Tac-Toe 📘			Medium
347	Top K Frequent Elements			Medium
346	Moving Average from Data Stream 📘			Easy
345	Reverse Vowels of a String			Easy
344	Reverse String	ruby		Easy
343	Integer Break	ruby		Medium
342	Power of Four			Easy
341	Flatten Nested List Iterator			Medium
340	Longest Substring with At Most K Distinct Characters 📘			Hard
339	Nested List Weight Sum 📘			Easy
338	Counting Bits	ruby		Medium
337	House Robber III	ruby		Medium
336	Palindrome Pairs			Hard
335	Self Crossing			Hard
334	Increasing Triplet Subsequence			Medium
333	Largest BST Subtree 📘			Medium
332	Reconstruct Itinerary			Medium
331	Verify Preorder Serialization of a Binary Tree	ruby		Medium
330	Patching Array			Hard
329	Longest Increasing Path in a Matrix			Hard
328	Odd Even Linked List	ruby		Medium
327	Count of Range Sum			Hard
326	Power of Three	ruby		Easy
325	Maximum Size Subarray Sum Equals k 📘			Medium
324	Wiggle Sort II			Medium
323	Number of Connected Components in an Undirected Graph 📘			Medium
322	Coin Change			Medium
321	Create Maximum Number			Hard
320	Generalized Abbreviation 📘			Medium
319	Bulb Switcher			Medium
318	Maximum Product of Word Lengths			Medium
317	Shortest Distance from All Buildings 📘			Hard
316	Remove Duplicate Letters			Hard
315	Count of Smaller Numbers After Self			Hard
314	Binary Tree Vertical Order Traversal 📘			Medium
313	Super Ugly Number	ruby		Medium
312	Burst Balloons			Hard
311	Sparse Matrix Multiplication 📘			Medium
310	Minimum Height Trees			Medium
309	Best Time to Buy and Sell Stock with Cooldown			Medium
308	Range Sum Query 2D - Mutable 📘			Hard
307	Range Sum Query - Mutable			Medium
306	Additive Number			Medium
305	Number of Islands II 📘			Hard
304	Range Sum Query 2D - Immutable			Medium
303	Range Sum Query - Immutable	ruby		Easy
302	Smallest Rectangle Enclosing Black Pixels 📘			Hard
301	Remove Invalid Parentheses			Hard
300	Longest Increasing Subsequence			Medium
299	Bulls and Cows			Medium
298	Binary Tree Longest Consecutive Sequence 📘			Medium
297	Serialize and Deserialize Binary Tree	ruby		Hard
296	Best Meeting Point 📘			Hard
295	Find Median from Data Stream			Hard
294	Flip Game II 📘			Medium
293	Flip Game 📘			Easy
292	Nim Game			Easy
291	Word Pattern II 📘			Hard
290	Word Pattern			Easy
289	Game of Life			Medium
288	Unique Word Abbreviation 📘			Medium
287	Find the Duplicate Number	ruby		Medium
286	Walls and Gates 📘			Medium
285	Inorder Successor in BST 📘			Medium
284	Peeking Iterator			Medium
283	Move Zeroes			Easy
282	Expression Add Operators			Hard
281	Zigzag Iterator 📘			Medium
280	Wiggle Sort 📘			Medium
279	Perfect Squares			Medium
278	First Bad Version	ruby		Easy
277	Find the Celebrity 📘			Medium
276	Paint Fence 📘			Easy
275	H-Index II			Medium
274	H-Index			Medium
273	Integer to English Words			Hard
272	Closest Binary Search Tree Value II 📘			Hard
271	Encode and Decode Strings 📘			Medium
270	Closest Binary Search Tree Value 📘			Easy
269	Alien Dictionary 📘			Hard
268	Missing Number			Easy
267	Palindrome Permutation II 📘			Medium
266	Palindrome Permutation 📘			Easy
265	Paint House II 📘			Hard
264	Ugly Number II	ruby		Medium
263	Ugly Number	ruby		Easy
261	Graph Valid Tree 📘			Medium
260	Single Number III			Medium
259	3Sum Smaller 📘			Medium
258	Add Digits			Easy
257	Binary Tree Paths			Easy
256	Paint House 📘			Easy
255	Verify Preorder Sequence in Binary Search Tree 📘			Medium
254	Factor Combinations 📘			Medium
253	Meeting Rooms II 📘			Medium
252	Meeting Rooms 📘			Easy
251	Flatten 2D Vector 📘			Medium
250	Count Univalue Subtrees 📘			Medium
249	Group Shifted Strings 📘			Medium
248	Strobogrammatic Number III 📘			Hard
247	Strobogrammatic Number II 📘			Medium
246	Strobogrammatic Number 📘			Easy
245	Shortest Word Distance III 📘			Medium
244	Shortest Word Distance II 📘			Medium
243	Shortest Word Distance 📘			Easy
242	Valid Anagram	ruby		Easy
241	Different Ways to Add Parentheses			Medium
240	Search a 2D Matrix II	ruby		Medium
239	Sliding Window Maximum			Hard
238	Product of Array Except Self			Medium
237	Delete Node in a Linked List			Easy
236	Lowest Common Ancestor of a Binary Tree	ruby		Medium
235	Lowest Common Ancestor of a Binary Search Tree	ruby		Easy
234	Palindrome Linked List			Easy
233	Number of Digit One			Hard
232	Implement Queue using Stacks			Easy
231	Power of Two			Easy
230	Kth Smallest Element in a BST	ruby		Medium
229	Majority Element II	ruby		Medium
228	Summary Ranges	javascript		Medium
227	Basic Calculator II			Medium
226	Invert Binary Tree			Easy
225	Implement Stack using Queues			Easy
224	Basic Calculator	ruby		Hard
223	Rectangle Area			Medium
222	Count Complete Tree Nodes	ruby		Medium
221	Maximal Square			Medium
220	Contains Duplicate III			Medium
219	Contains Duplicate II	ruby		Easy
218	The Skyline Problem			Hard
217	Contains Duplicate			Easy
216	Combination Sum III			Medium
215	Kth Largest Element in an Array	ruby		Medium
214	Shortest Palindrome			Hard
213	House Robber II			Medium
212	Word Search II			Hard
211	Add and Search Word - Data structure design			Medium
210	Course Schedule II			Medium
209	Minimum Size Subarray Sum	ruby		Medium
208	Implement Trie (Prefix Tree)			Medium
207	Course Schedule			Medium
206	Reverse Linked List			Easy
205	Isomorphic Strings			Easy
204	Count Primes			Easy
203	Remove Linked List Elements			Easy
202	Happy Number	ruby		Easy
201	Bitwise AND of Numbers Range			Medium
200	Number of Islands			Medium
199	Binary Tree Right Side View	ruby		Medium
198	House Robber			Easy
191	Number of 1 Bits	ruby		Easy
190	Reverse Bits			Easy
189	Rotate Array			Easy
188	Best Time to Buy and Sell Stock IV			Hard
187	Repeated DNA Sequences			Medium
186	Reverse Words in a String II 📘			Medium
179	Largest Number			Medium
174	Dungeon Game	ruby		Hard
173	Binary Search Tree Iterator			Medium
172	Factorial Trailing Zeroes	ruby		Easy
171	Excel Sheet Column Number			Easy
170	Two Sum III - Data structure design 📘			Easy
169	Majority Element			Easy
168	Excel Sheet Column Title			Easy
167	Two Sum II - Input array is sorted	ruby		Easy
166	Fraction to Recurring Decimal	ruby		Medium
165	Compare Version Numbers			Medium
164	Maximum Gap	ruby		Hard
163	Missing Ranges 📘			Medium
162	Find Peak Element	ruby		Medium
161	One Edit Distance 📘			Medium
160	Intersection of Two Linked Lists	javascript		Easy
159	Longest Substring with At Most Two Distinct Characters 📘			Hard
158	Read N Characters Given Read4 II - Call multiple times 📘			Hard
157	Read N Characters Given Read4 📘			Easy
156	Binary Tree Upside Down 📘			Medium
155	Min Stack			Easy
154	Find Minimum in Rotated Sorted Array II	ruby		Hard
153	Find Minimum in Rotated Sorted Array	ruby		Medium
152	Maximum Product Subarray			Medium
151	Reverse Words in a String			Medium
150	Evaluate Reverse Polish Notation	ruby		Medium
149	Max Points on a Line			Hard
148	Sort List	ruby		Medium
147	Insertion Sort List			Medium
146	LRU Cache			Hard
145	Binary Tree Postorder Traversal			Hard
144	Binary Tree Preorder Traversal	ruby		Medium
143	Reorder List			Medium
142	Linked List Cycle II			Medium
141	Linked List Cycle			Easy
140	Word Break II			Hard
139	Word Break			Medium
138	Copy List with Random Pointer			Medium
137	Single Number II			Medium
136	Single Number			Easy
135	Candy			Hard
134	Gas Station			Medium
133	Clone Graph			Medium
132	Palindrome Partitioning II			Hard
131	Palindrome Partitioning	ruby		Medium
130	Surrounded Regions			Medium
129	Sum Root to Leaf Numbers			Medium
128	Longest Consecutive Sequence	ruby		Hard
127	Word Ladder			Medium
126	Word Ladder II			Hard
125	Valid Palindrome			Easy
124	Binary Tree Maximum Path Sum			Hard
123	Best Time to Buy and Sell Stock III			Hard
122	Best Time to Buy and Sell Stock II			Easy
121	Best Time to Buy and Sell Stock			Easy
120	Triangle			Medium
119	Pascal's Triangle II			Easy
118	Pascal's Triangle			Easy
117	Populating Next Right Pointers in Each Node II			Medium
116	Populating Next Right Pointers in Each Node			Medium
115	Distinct Subsequences			Hard
114	Flatten Binary Tree to Linked List	ruby		Medium
113	Path Sum II			Medium
112	Path Sum			Easy
111	Minimum Depth of Binary Tree	ruby		Easy
110	Balanced Binary Tree	ruby		Easy
109	Convert Sorted List to Binary Search Tree			Medium
108	Convert Sorted Array to Binary Search Tree	ruby		Easy
107	Binary Tree Level Order Traversal II	ruby		Easy
106	Construct Binary Tree from Inorder and Postorder Traversal			Medium
105	Construct Binary Tree from Preorder and Inorder Traversal			Medium
104	Maximum Depth of Binary Tree			Easy
103	Binary Tree Zigzag Level Order Traversal			Medium
102	Binary Tree Level Order Traversal			Medium
101	Symmetric Tree	ruby		Easy
100	Same Tree			Easy
99	Recover Binary Search Tree			Hard
98	Validate Binary Search Tree			Medium
97	Interleaving String			Hard
96	Unique Binary Search Trees	ruby		Medium
95	Unique Binary Search Trees II			Medium
94	Binary Tree Inorder Traversal			Medium
93	Restore IP Addresses			Medium
92	Reverse Linked List II			Medium
91	Decode Ways			Medium
90	Subsets II	ruby		Medium
89	Gray Code	ruby		Medium
88	Merge Sorted Array			Easy
87	Scramble String			Hard
86	Partition List			Medium
85	Maximal Rectangle			Hard
84	Largest Rectangle in Histogram			Hard
83	Remove Duplicates from Sorted List			Easy
82	Remove Duplicates from Sorted List II			Medium
81	Search in Rotated Sorted Array II			Medium
80	Remove Duplicates from Sorted Array II			Medium
79	Word Search			Medium
78	Subsets	ruby		Medium
77	Combinations			Medium
76	Minimum Window Substring			Hard
75	Sort Colors			Medium
74	Search a 2D Matrix	ruby		Medium
73	Set Matrix Zeroes			Medium
72	Edit Distance			Hard
71	Simplify Path			Medium
70	Climbing Stairs	ruby		Easy
69	Sqrt(x)			Easy
68	Text Justification			Hard
67	Add Binary			Easy
66	Plus One	ruby		Easy
65	Valid Number			Hard
64	Minimum Path Sum			Medium
63	Unique Paths II			Medium
62	Unique Paths			Medium
61	Rotate List	ruby		Medium
60	Permutation Sequence			Medium
59	Spiral Matrix II			Medium
58	Length of Last Word			Easy
57	Insert Interval			Hard
56	Merge Intervals			Medium
55	Jump Game			Medium
54	Spiral Matrix			Medium
53	Maximum Subarray			Easy
52	N-Queens II			Hard
51	N-Queens	ruby		Hard
50	Pow(x, n)			Medium
49	Group Anagrams			Medium
48	Rotate Image			Medium
47	Permutations II			Medium
46	Permutations			Medium
45	Jump Game II			Hard
44	Wildcard Matching			Hard
43	Multiply Strings			Medium
42	Trapping Rain Water			Hard
41	First Missing Positive			Hard
40	Combination Sum II			Medium
39	Combination Sum			Medium
38	Count and Say			Easy
37	Sudoku Solver			Hard
36	Valid Sudoku			Medium
35	Search Insert Position			Easy
34	Search for a Range			Medium
33	Search in Rotated Sorted Array			Medium
32	Longest Valid Parentheses	ruby		Hard
31	Next Permutation			Medium
30	Substring with Concatenation of All Words			Hard
29	Divide Two Integers			Medium
28	Implement strStr()	ruby		Easy
27	Remove Element			Easy
26	Remove Duplicates from Sorted Array	ruby		Easy
25	Reverse Nodes in k-Group			Hard
24	Swap Nodes in Pairs			Medium
23	Merge k Sorted Lists			Hard
22	Generate Parentheses			Medium
21	Merge Two Sorted Lists			Easy
20	Valid Parentheses			Easy
19	Remove Nth Node From End of List	ruby		Medium
18	4Sum	ruby		Medium
17	Letter Combinations of a Phone Number			Medium
16	3Sum Closest	javascript		Medium
15	3Sum			Medium
14	Longest Common Prefix	ruby		Easy
13	Roman to Integer			Easy
12	Integer to Roman	ruby		Medium
11	Container With Most Water			Medium
10	Regular Expression Matching			Hard
9	Palindrome Number			Easy
8	String to Integer (atoi)	ruby		Medium
7	Reverse Integer	ruby		Easy
6	ZigZag Conversion			Medium
5	Longest Palindromic Substring			Medium
4	Median of Two Sorted Arrays			Hard
3	Longest Substring Without Repeating Characters	ruby go		Medium
2	Add Two Numbers			Medium
1	Two Sum	ruby		Easy