Code

LeetCode Problems

#	Title	Solution	Difficulty
1	Two Sum	C++ Java	easy
2	Add Two Numbers	C++ Java	medium
3	Longest Substring Without Repeating Characters	C++ Java	medium
4	Median of Two Sorted Arrays	C++ Java	hard
5	Longest Palindromic Substring	C++ Java	medium
6	ZigZag Conversion	C++ Java	medium
7	Reverse Integer	C++ Java	easy
8	String to Integer (atoi)	C++ Java	medium
10	Regular Expression Matching	Java	hard
15	3Sum	C++ Java	medium
16	3Sum Closest	C++ Java	medium
17	Letter Combinations of a Phone Number	C++ Java	medium
18	4Sum	C++	medium
19	Remove Nth Node From End of List	C++	medium
20	Valid Parentheses	C++	easy
21	Merge Two Sorted Lists	C++	easy
22	Generate Parentheses	C++ Java	medium
23	Merge k Sorted Lists	C++ Java	hard
24	Swap Nodes in Pairs	C++ Java	medium
25	Reverse Nodes in k-Group	C++ Java	hard
29	Divide Two Integers	C++ Java	medium
31	Next Permutation	C++	medium
32	Longest Valid Parentheses	C++	hard
33	Search in Rotated Sorted Array	C++ Java	medium
34	Find First and Last Position of Element in Sorted Array	C++	medium
35	Search Insert Position	C++ Java	easy
36	Valid Sudoku	C++	medium
37	Sudoku Solver	Java	hard
39	Combination Sum	C++ Java	medium
40	Combination Sum II	C++ Java	medium
41	First Missing Positive	C++	hard
42	Trapping Rain Water	C++	hard
44	Wildcard Matching	C++	hard
45	Jump Game II	C++ Java	hard
46	Permutation	C++ Java	medium
47	Permutations II	C++ Java	medium
48	Rotate Image	C++	medium
49	Group Anagrams	C++ Java	medium
51	N-Queens	Java	hard
53	Maximum Subarray	C++ Java	easy
54	Spiral Matrix	C++	medium
55	Jump Game	Java	medium
56	Merge Intervals	C++	medium
57	Insert Interval	C++	medium
61	Rotate List	C++ Java	medium
62	Unique Paths	C++	medium
63	Unique Paths II	C++	medium
64	Minimum Path Sum	C++	medium
69	Sqrt(x)	Java	easy
71	Simplify Path	C++	medium
72	Edit Distance	C++ Java	hard
74	Search a 2D Matrix	C++ Java	medium
75	Sort Colors	Java	medium
76	Minimum Window Substring	C++	hard
77	Combinations	C++ Java	medium
78	Subsets	C++ Java	medium
79	Word Search	C++ Java	medium
80	Remove Duplicates from Sorted Array II	C++	medium
81	Search in Rotated Sorted Array II	C++ Java	medium
82	Remove Duplicates from Sorted List II	C++	medium
83	Remove Duplicates from Sorted List	C++	easy
84	Largest Rectangle in Histogram	C++	hard
85	Maximal Rectangle	C++	hard
86	Partition List	C++	medium
88	Merge Sorted Array	C++	easy
90	Subsets II	C++ Java	medium
91	Decode Ways	C++	medium
92	Reverse Linked List II	C++	medium
93	Restore IP Addresses	C++ Java	medium
95	Unique Binary Search Trees II	C++	medium
96	Unique Binary Search Trees	C++	medium
98	Validate Binary Search Tree	C++	medium
99	Recover Binary Search Tree	C++ Java	hard
102	Binary Tree Level Order Traversal	C++	medium
103	Binary Tree Zigzag Level Order Traversal	C++ Java	medium
105	Construct Binary Tree from Preorder and Inorder Traversal	C++ Java	medium
106	Construct Binary Tree from Inorder and Postorder Traversal	C++ Java	medium
108	Convert Sorted Array to Binary Search Tree	C++ Java	easy
109	Convert Sorted List to Binary Search Tree	C++ Java	medium
112	Path Sum	C++ Java	easy
113	Path Sum II	C++ Java	medium
114	Flatten Binary Tree to Linked List	C++ Java	medium
115	Distinct Subsequences	C++	hard
116	Populating Next Right Pointers in Each Node	C++ Java	meduim
117	Populating Next Right Pointers in Each Node 2	C++ Java	medium
120	Triangle	C++	medium
121	Best Time to Buy and Sell Stock	C++	easy
126	Word Ladder II	Java	hard
127	Word Ladder	Java	medium
129	Sum Root to Leaf Numbers	Java	medium
133	Clone Graph	Java	medium
139	Word Break	Java	medium
140	Word Break II	Java	hard
152	Maximum Product Subarray	Java	medium
153	Find Minimum in Rotated Sorted Array	Java	medium
154	Find Minimum in Rotated Sorted Array II	Java	hard
159	Longest Substring with At Most Two Distinct Characters	Java	medium
162	Find Peak Element	Java	medium
167	Two Sum II	Java	easy
198	House Robber	Java	easy
199	Binary Tree Right Side View	Java	medium
200	Number of Islands	Java	medium
207	Course Schedule	Java	medium
208	Implement Trie (Prefix Tree)	Java	medium
210	Course Schedule II	Java	medium
211	Design Add and Search Words Data Structure	Java	medium
212	Word Search II	Java	hard
213	House Robber II	Java	medium
215	Kth Largest Element in an Array	Java	medium
216	Combination Sum III	Java	medium
218	The Skyline Problem	Java	hard
222	Count Complete Tree Nodes	Java	medium
235	Lowest Common Ancestor of a Binary Search Tree	Java	easy
236	Lowest Common Ancestor of a Binary Tree	Java	medium
239	Sliding Window Maximum	Java	medium
240	Search a 2D Matrix II	Java	medium
250	Count Univalue Subtree	Java	medium
252	Meeting Room	Java	easy
253	Meeting Rooms II	Java	medium
255	Verify Preorder Sequence in Binary Search Tree	Java	medium
261	Graph Valid Tree	Java	medium
267	Palindrome Permutation II	C++	medium
268	Missing Number	Java	easy
269	Alien Dictionary	Java	hard
270	Closest Binary Search Tree Value	Java	medium
271	Encode and Decode Strings	Java	medium
272	Closest Binary Search Tree Value II	Java	medium
274	H Index	Java	medium
275	H Index II	Java	medium
277	Find the Celebrity	Java	medium
285	Inorder Successor in BST	Java	medium
291	Word Pattern II	Java	medium
297	Serialize and Deserialize Binary Tree	Java	hard
300	Longest Increasing Subsequence	Java	medium
305	Number of Islands II	Java	hard
314	Binary Tree Vertical Order Traversal	Java	medium
315	Count of Smaller Numbers After Self	Java	hard
322	Coin Change	Java	medium
323	Number of Connected Components in an Undirected Graph	Java	medium
333	Largest BST Subtree	Java	medium
337	House Robber III	Java	medium
340	Longest Substring with At Most K Distinct Characters	Java	hard
347	Top K Frequent Elements	Java	medium
360	Sort Transformed Array	Java	medium
377	Combination Sum IV	C++ Java	medium
426	Convert Binary Search Tree to Sorted Doubly Linked List	Java	medium
428	Serialize and Deserialize N-ary Tree	Java	hard
437	Path Sum III	Java	medium
438	Find All Anagrams in a String	Java	medium
445	Add Two Numbers II	Java	medium
450	Delete Node in a BST	Java	medium
463	Island Perimeter	Java	easy
494	Target Sum	C++	medium
510	Inorder Successor in BST II	Java	medium
518	Coin Change 2	Java	medium
540	Single Element in a Sorted Array	Java	medium
542	01 Matrix	Java	medium
545	Boundary of Binary Tree	Java	medium
547	Friend Circles	Java	medium
611	Valid Triangle Number	Java	medium
617	Merge Two Binary Trees	Java	easy
632	Smallest Range Covering Elements from K Lists	Java	hard
640	Solve the Equation	Java	medium
*653	Two Sum IV - Input is a BST	Java	easy
658	Find K Closest Elements	Java	medium
668	Kth Smallest Number in Multiplication Table	Java	hard
695	Max Area of Island	Java	medium
733	Flood Fill	Java	easy
744	Find Smallest Letter Greater Than Target	Java	easy
773	Sliding Puzzle	Java	hard
785	Is Graph Bipartite	Java	medium
802	Find Eventual Safe States	Java	medium
865	Smallest Subtree with all the Deepest Nodes	Java	medium
958	Check Completeness of a Binary Tree	Java	medium
994	Rotting Oranges	Java	medium
997	Find the Town Judge	Java	easy
1008	Construct Binary Search Tree from Preorder Traversal	Java	medium
1060	Missing Element in Sorted Array	Java	medium
1095	Find in Mountain Array	Java	hard
1100	Find K-Length Substrings With No Repeated Characters	Java	medium
1228	Missing Number in Arithmetic Progression	Java	easy
1229	Meeting Scheduler	Java	medium
1254	Number of Closed Islands	C++	medium
1306	Jump Game III	Java	medium
1584	Min Cost to Connect All Points	Java	medium
1602	Find Nearest Right Node in Binary Tree	Java	medium
1727	Largest Submatrix With Rearrangements	C++	medium

Fun Problems

topic	Title	Solution
binary search	Find Local Minimum	Java
binary search	Random Generator	Java
binary search	Smaller Equal in 2D Matrix	Java
binary search	Larger in 2D Matrix	Java
sampling	Reservoir Sampling	Java
sampling	General Reservoir Sampling	Java
sampling	Sampling in Binary Tree	Java
sorting	Selection Sort	Java
sorting	Bubble Sort	Java
sorting	Insertion Sort	Java
sorting	Heap Sort	Java
sorting	Merge Sort	Java
sorting	Quick Sort	Java
sorting	Quick Select	Java
sorting	Rainbow Sort with K Color	Java
two pointers	Number of Pairs of Two Sum	Java
two pointers	Two Sum from Two Arrays	Java
two pointers	Number of Triples Smaller than Target	Java
two pointers	Three Sum in BST	Java
prefix sum	Subarray Sum Closest to Target	Java
sliding window	Most Online Virtual Machines	Java
sliding window	Max weight Sum(follow up)	Java
sliding window	Product of K Sliding Window	Java
sliding window	Number of Pairs Smaller or Equal to Target	Java
sliding window	Number of Pairs Difference Smaller or Equal to Target in Two Arrays	Java
sliding window	Minimal Length of Subarray Sum Larger Than Target	Java
sliding window	Most Frequent of K Sliding Window	Java
sliding window	Count Time for Tasks with Cool Down without Changing Order	Java
sliding window	Size of Longest Subarray with Any Absolute Difference Smaller than Target	Java
string	Reverse Sentence in Size K	Java
string	Decode Parenthesis String	Java
string	Add String	Java
string	Subtract String	Java
string	Form Target String with Source String	Java
linked list	Reverse a Doubly Linked List	Java
linked list	Find Middle Node of Linked List	Java
linked list	Merged Lists	C++ Java
linked list	Reverse LinkedList in K Group	Java
tree	Inorder Traversal in Binary Tree	Java
tree	Preorder Traversal in Binary Tree	Java
tree	Postorder Traversal in Binary Tree	Java
tree	Kth Largest Element in BST	Java
tree	Binary Tree Top View or Bottom View	Java
tree	Populate Next Pointer	Java
tree	Sum of All Leaf Nodes in n-ary tree with O(1) space	Java
tree	Visible Nodes in Tree	Java
tree	Sum Leaf to Root Numbers	Java
tree	Equivalent Trees	Java
tree	Outside to Inside	Java
tree	Remove All Zero Subtree	Java
tree	Remove All Nodes with Only One Child	Java
tree	Or of Two Binary Trees	Java
tree	And Operation on Quadtree	Java
tree	Retain Nodes in Range for BST	Java
tree	Collect Leaf and Remove	Java
tree	Determine Perfect Tree	Java
tree	Check Full Tree	Java
tree	Lowest Common Ancestor May Not Exist	Java
tree	Lowest Common Ancestor With Parent Pointer	Java
tree	K Nodes Lowest Common Ancestor	Java
tree	Lowest Common Ancestor in K-nary tree	Java
tree	K Nodes Lowest Common Ancestor in K-nary Tree	Java
tree	Number of Edges Between Two Nodes	Java
tree	Change Value of Each Node of BST to Prefixsum	Java
tree	Sum of Nested Integer Weighted by Depth	Java
tree	K Closest to Target in BST	Java
tree	Find Most Frequent Element in BST	Java
tree	Divide BST Using Pivot	Java
tree path	Up Down Any to Any Largest Path Sum	Java
tree path	Any to Any Largest Path Sum	Java
tree path	Path Sum to Target	Java
tree path	Path Product to Target	Java
tree path	Longest Increasing Path	Java
tree path	Hours of Burn Down the Whole Tree	Java
serialize tree	Convert 3-ary Tree to Singly Link List	Java
serialize tree	Convert BST to Sorted Circular Doubly Linked List	Java
serialize tree	Serialize and Deserialize String Type Tree	Java
construct tree	Given BST Preorder Return Postorder	Java
construct tree	Construct Binary Tree with Levelorder and Inorder	Java
construct tree	Construct Binary Search Tree With Level Order	Java
construct tree	Construct Binary Tree with Special Signal	Java
construct tree	Construct N-ary Tree with Preorder and Postorder	Java
construct tree	Construct N-ary Tree with Parent Id Node	Java
hybrid data structure	Top K Frequency Problem	Java
hybrid data structure	K-diff Sorted Array	Java
hybrid data structure	Most Recent k URLs	Java
backtracking	All Combinations Sum to Target with Size k	Java
backtracking	Make Work Schedule	Java
backtracking	Keep Distance for Number of Element	Java
backtracking	Possible Score Sequence Football Game	Java
graph	Basic DFS	Java
graph	Basic BFS	Java
graph	Deep Copy an Undirected Graph	Java
graph	Determine if Graph Has Cycle	Java
graph	Determine if Directed Graph is Tree	Java
graph	All Nodes Reached in K Steps	Java
graph	All Nodes Reached by exactly K Steps	Java
graph	Top K M levels of Similar Songs	Java
graph	Divide People with Whom They Want to Work With	Java
graph	Traverse All Places with One Cycle	Java
graph	Bi-Directional BFS	Java
topological order	Topological Order	Java
topological order	Get All Topological Order	Java
topological order	Compile Source File	Java
dp	Return Maximum Subarray	C++
dp	Split Words	Java
dp	Largest Square Sum	Java
dp	Max weight Sum	Java
dp	Maximum Subset Sum	C++
dp	Cross Bridge	C++
intervals	Common Free Intervals for Employees	Java

Data Structures

Data Structures	Implementation
Queue	Java
Min Heap / PriorityQueue	Java
HashMap	Java
Tree Inorder Iterator	Java
Binary Search Tree Inorder Asc/Des Iterator	Java
Tree Preorder Iterator	Java
Tree Postorder Iterator	Java
Union Find	Java
Trie	Java
Segment Tree	Java

Designs

Designs	Implementation
Browser History	Java
Design Add Remove Find Random APIs in O(1) time	Java
Auto Spell Correction	Java