5. Longest Palindromic Substring

(Reference: https://leetcode.com/problems/longest-palindromic-substring/solution/)

Solution	Date
Longest Common Substring	6/24
Brute Force	6/24
Dynamic Programming	8/14
Expand Around Center	8/12

92. Reverse Linked List II

Solution	Date
Head->Rev->End	7/5

46. Permutations

Solution	Date
BackTracking	7/7
Dfs	7/7

47. Permutations II

Solution	Date
BackTracking	7/7
Dfs

28. Implement strStr()

Solution	Date
BruteForce	7/9
Kmp

39. Combination Sum

Solution	Date
Dfs	7/10

16. 3Sum Closest

Solution	Date
Two Pointers	7/11

48. Rotate Image

Solution	Date
Sym->UpDown	7/12

17. Letter Combinations of a Phone Number

Solution	Date
Dfs	7/12
Bfs

38. Count and Say

Solution	Date
Brute Force	7/12

22. Generate Parentheses

Solution	Date
Dfs	7/15

(Other Solutions, Reference: https://leetcode.com/problems/generate-parentheses/solution/)

Solution	Date
BackTracking	7/15
Closure Number
Dynamic Programming

8. String to Integer (atoi)

Solution	Date
	7/18

24. Swap Nodes in Pairs

Solution	Date
Iterative	7/19
Recursive	7/19

(Other Solutions, Reference: https://leetcode.com/problems/swap-nodes-in-pairs/discuss/11019/7-8-lines-C++-Python-Ruby?page=2)

Solution	Date
pointer to pointer	7/19

(Other Solutions, Reference: APAS)

Solution	Date
swap function (IterII)	7/19
break swap (IterIII)	7/19

29. Divide Two Integers

Solution	Date
LeftShift	7/20
RightShift

(Other Solutions, Reference: https://leetcode.com/problems/divide-two-integers/discuss/13407/Detailed-Explained-8ms-C++-solution)

Solution	Date
Use Remainder	7/21

33. Search in Rotated Sorted Array

Solution	Date
Revise Binary Search	7/22

(Other Solutions, Reference: https://leetcode.com/problems/search-in-rotated-sorted-array/discuss/14425/Concise-O(log-N)-Binary-search-solution)

Solution	Date
Find Smallest First	7/22

(Other Solutions, Reference: https://leetcode.com/problems/search-in-rotated-sorted-array/discuss/14435/Clever-idea-making-it-simple?page=2)

Solution	Date
Infinity	7/24

153. Find Minimum in Rotated Sorted Array

Solution	Date
MidHigh	7/24
MidLow	7/24

34. Find First and Last Position of Element in Sorted Array

Solution	Date
Expand if duplicate	7/24

(Other Solutions, Reference: https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/discuss/)

Solution	Date
Divide & Conquer

(Other Solutions, Reference: https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/discuss/14699/Clean-iterative-solution-with-two-binary-searches-(with-explanation))

Solution	Date
Two Binary Search

(Other Solutions, Reference: https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/solution/)

36. Valid Sudoku

Solution	Date
Row Col Box	7/25

(Other Solutions, Reference: https://leetcode.com/problems/valid-sudoku/discuss/15464/My-short-solution-by-C++.-O(n2))

Solution	Date
Row Col Box (One Loop)

40. Combination Sum II

Solution	Date
Dfs	7/25

43. Multiply Strings

Solution	Date
Multiply	7/26

(Other Solutions, Reference: https://leetcode.com/problems/multiply-strings/discuss/17646/Brief-C++-solution-using-only-strings-and-without-reversal)

Solution	Date
Multiply - Preallocate	7/26

(Other Solutions, Reference: https://leetcode.com/problems/multiply-strings/discuss/17605/Easiest-JAVA-Solution-with-Graph-Explanation)

Solution	Date
MultiplyByPair

50. Pow(x, n)

Solution	Date
divide by 2 (Need Fix!)	7/26

(Other Solutions, Reference: https://leetcode.com/problems/powx-n/discuss/19546/Short-and-easy-to-understand-solution)

Solution	Date
multiply by 2	7/26

(Other Solutions, Reference: https://leetcode.com/problems/powx-n/discuss/19544/5-different-choices-when-talk-with-interviewers)

Solution	Date
Nest MyPow
Iterative
Bit Op

53. Maximum Subarray

Solution	Date
Scan until less than zero	7/27

(Other Solutions, Reference: https://leetcode.com/problems/maximum-subarray/discuss/20193/DP-solution-and-some-thoughts)

Solution	Date
DP	7/27

62. Unique Paths

Solution	Date
Dfs (TLE)	7/27
Recursive
DP	7/27

(Other Solutions, Reference: https://leetcode.com/problems/unique-paths/discuss/22954/0ms-5-lines-DP-Solution-in-C++-with-Explanations)

Solution	Date
Optimize DP (Space: O(min(m,n))	7/27

(Other Solutions, Reference: https://leetcode.com/problems/unique-paths/discuss/22958/Math-solution-O(1)-space?page=2)

Solution	Date
Combinatorial	7/27

63. Unique Paths II

Solution	Date
DP	7/27

64. Minimum Path Sum

Solution	Date
Dfs(TLE)	7/30
DP	7/30
DP (With One Array (#62)
DP	7/30

88. Merge Sorted Array

Solution	Date
Brute Force	8/2

(Other Solutions, Reference: https://leetcode.com/problems/merge-sorted-array/discuss/29522/This-is-my-AC-code-may-help-you)

Solution	Date
Check From Tail	8/2

61. Rotate List

Solution	Date
Length, Fast, Slow	8/2

(Other Solutions, Reference: https://leetcode.com/problems/rotate-list/discuss/22735/My-clean-C++-code-quite-standard-(find-tail-and-reconnect-the-list))

Solution	Date
Length, Tail

54. Spiral Matrix

Solution	Date
Right Down Left Up Check	8/2

(Other Solutions, Reference: https://leetcode.com/problems/spiral-matrix/discuss/20599/Super-Simple-and-Easy-to-Understand-Solution)

Solution	Date
Right Down Left Up

55. Jump Game

Solution	Date
Update Index	8/3

(Other Solutions, Reference: https://leetcode.com/problems/jump-game/discuss/20900/Simplest-O(N)-solution-with-constant-space)

Solution	Date
Backward	8/3

(Other Solutions, Reference: https://leetcode.com/problems/jump-game/solution/)

Solution	Date
DP ( top-down )
DP ( bottom-up )

71. Simplify Path

Solution	Date
Brute Force	8/3

(Other Solutions, Reference: https://leetcode.com/problems/simplify-path/discuss/25773/My-O(n)-AC-code-.-just-need-to-handle-two-special-cases.)

Solution	Date
Brute Force (Simpilfy Special Case Comparison)

(Other Solutions, Reference: https://leetcode.com/problems/simplify-path/discuss/25680/C++-10-lines-solution)

Solution	Date
GetLine

56. Merge Intervals

Solution	Date
Sort -> Compare	8/3

(Other Solutions, Reference: https://leetcode.com/problems/merge-intervals/description/)

59. Spiral Matrix II

Solution	Date
Right Down Left Up Check	8/3

(Other Solutions, Reference: https://leetcode.com/problems/spiral-matrix-ii/discuss/22282/4-9-lines-Python-solutions)

60. Permutation Sequence

Solution	Date
NextPermutation	8/3

(Other Solutions, Reference: https://leetcode.com/problems/permutation-sequence/discuss/22507/%22Explain-like-I'm-five%22-Java-Solution-in-O(n))

Solution	Date
Factorial	8/6

69. Sqrt(x)

Solution	Date
Binary Search	8/6

100. Same Tree

(Reference: https://leetcode.com/problems/same-tree/discuss/32687/Five-line-Java-solution-with-recursion)

Solution	Date
Inorder	8/6
Preorder
Postorder

70. Climbing Stairs

Solution	Date
Combination (n = 44 Fail)

(Other Solutions, Reference: https://leetcode.com/problems/climbing-stairs/discuss/25299/Basically-it's-a-fibonacci.)

Solution	Date
Fibonacci	8/8

125. Valid Palindrome

Solution	Date
Head & Tail	8/14

516. Longest Palindromic Subsequence

Solution	Date
Dynamic Programming	8/15

Lintcode-458.LastPositionofTarget

Solution	Date
Brute Force	8/17

(Other Solutions, Reference: https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/discuss/14699/Clean-iterative-solution-with-two-binary-searches-(with-explanation)?page=4)

Solution	Date
Revised Binary Search	8/17

LintCode-585. Maximum Number in Mountain Sequence

Solution	Date
Revised Binary Search	8/17

658. Find K Closest Elements

Solution	Date
Binary Search Condition 1	8/18
Binary Search Condition 2	8/18
Binary Search Condition 3	8/18
Binary Search Condition 4	8/18

LintCode-447. Search in a Big Sorted Array

Solution	Date
Revised Binary Search	8/18

162. Find Peak Element

Solution	Date
Iter1	8/18

(Other Solutions, Reference: https://leetcode.com/problems/find-peak-element/solution/)

Solution	Date
Iter2
Sequential
Recursive

278. First Bad Version

Solution	Date
Revised Binary Search	8/18

876. Middle of the Linked List

(Other Solutions, Reference: https://leetcode.com/problems/middle-of-the-linked-list/solution/)

Solution	Date
Two Pointers	8/19

LintCode-228. Middle of Linked List

(Other Solutions, Reference: https://leetcode.com/problems/middle-of-the-linked-list/solution/)

Solution	Date
Two Pointers	8/19

283. Move Zeroes

Solution	Date
Swap	8/19

(Other Solutions, Reference: https://leetcode.com/problems/move-zeroes/solution/)

Solution	Date
Swap Optimize	8/19
Copy	8/19

LintCode-521. Remove Duplicate Numbers in Array

Solution	Date
Target and 2 pointers	8/19
Sort	8/19
Hash	8/19

75. Sort Colors

Solution	Date
Counting Sort In Place	8/19
Counting Sort Out Place	8/19
Two Pointers	8/19
Two Pointers Optimize	8/20

LintCode-143. Sort Colors II

Solution	Date
Count In Place	8/19
Two Pointers	8/20

LintCode-31. Partition Array

Solution	Date
Two Pointers	8/20

607. Two Sum III - Data structure design

Solution	Date
Hash Table	8/20

215. Kth Largest Element in an Array

Solution	Date
Quick Sort Half	8/21

200. Number of Islands

Solution	Date
Bfs	8/21
Bfs Optimize	8/22
Dfs
Union Find

102. Binary Tree Level Order Traversal

Solution	Date
Bfs Vector	8/24
Bfs Queue	8/24
Dfs

207. Course Schedule

(Reference: https://leetcode.com/problems/course-schedule/discuss/58509/18-22-lines-C++-BFSDFS-Solutions)

Solution	Date
Bfs Vector	8/24

(Other Solutions, Reference: https://leetcode.com/problems/course-schedule/discuss/58516/Easy-BFS-Topological-sort-Java)

Solution	Date
Bfs Queue	8/24
Dfs

LintCode-611. Knight Shortest Path

Solution	Date
Bfs Level	8/25

127. Word Ladder

(Reference: https://leetcode.com/problems/word-ladder/discuss/40707/Easy-76ms-C++-Solution-using-BFS)

Solution	Date
Bfs Level	8/25

444. Sequence Reconstruction

Solution	Date
Topological	8/26

297. Serialize and Deserialize Binary Tree

(Reference: https://leetcode.com/problems/serialize-and-deserialize-binary-tree/discuss/74252/Clean-C++-solution)

Solution	Date
Preorder	8/26

(Other Solutions, Reference: https://leetcode.com/problems/serialize-and-deserialize-binary-tree/discuss/74264/Short-and-straight-forward-BFS-Java-code-with-a-queue)

Solution	Date
Bfs

210. Course Schedule II

Solution	Date
Topological Sort	8/26

LintCode-127. Topological Sorting

Solution	Date
Topological Sort	8/26

133. Clone Graph

(Reference: https://leetcode.com/problems/clone-graph/discuss/42313/7-17-lines-C++-BFSDFS-Solutions)

Solution	Date
Bfs	8/26
Dfs

270. Closest Binary Search Tree Value

Solution	Date
Iterative	8/26
Iter Optimize	8/26
Recuresive	8/26

LintCode-596. Minimum Subtree

Solution	Date
Dfs Traverse	8/28

114. Flatten Binary Tree to Linked List

(Reference: https://leetcode.com/problems/flatten-binary-tree-to-linked-list/discuss/36977/My-short-post-order-traversal-Java-solution-for-share)

Solution	Date
PostOrder	8/29

110. Balanced Binary Tree

Solution	Date
Traverse	9/1

104. Maximum Depth of Binary Tree

Solution	Date
Bfs	9/1
Dfs	9/1

559. Maximum Depth of N-ary Tree

Solution	Date
Dfs	9/1
Bfs

230. Kth Smallest Element in a BST

Solution	Date
Count Left Elements	9/1

(Other Solutions, Reference: https://leetcode.com/problems/kth-smallest-element-in-a-bst/discuss/63660/3-ways-implemented-in-JAVA-(Python):-Binary-Search-in-order-iterative-and-recursive)

Solution	Date
Dfs Inorder	9/1

236. Lowest Common Ancestor of a Binary Tree

Solution	Date
Check Left Right	9/1

94. Binary Tree Inorder Traversal

Solution	Date
Recursive	9/3

(Other Solutions, Reference: https://leetcode.com/articles/binary-tree-inorder-traversal/)

Solution	Date
Iterative	9/3

599. Minimum Index Sum of Two Lists

Solution	Date
Hash map	9/3

564. Find the Closest Palindrome

(Reference: https://leetcode.com/problems/find-the-closest-palindrome/discuss/102396/C++-short-solution-only-need-to-compare-5-numbers)

Solution	Date
Find Candidates	9/3

(Other Solutions, Reference: https://leetcode.com/problems/find-the-closest-palindrome/solution/)

Solution	Date
Using Math

98. Validate Binary Search Tree

(Reference: https://leetcode.com/problems/validate-binary-search-tree/discuss/32112/Learn-one-iterative-inorder-traversal-apply-it-to-multiple-tree-questions-(Java-Solution)?page=2)

Solution	Date
Iter	9/3

272. Closest Binary Search Tree Value II

(Reference: https://leetcode.com/problems/closest-binary-search-tree-value-ii/discuss/70499/Java-5ms-iterative-following-hint-O(klogn)-time-and-space)

Solution	Date
Two Stack	9/4

131. Palindrome Partitioning

Solution	Date
Backtracking	9/4

77. Combinations

Solution	Date
Backtracking	9/4

78. Subsets

Solution	Date
Backtracking	9/4

90. Subsets II

Solution	Date
Backtracking	9/4
Iterative

140. Word Break II

Solution	Date
Backtracking (TLE)	9/4

443. String Compression

Solution	Date
Map	9/7
Two Pointers

139. Word Break

(Todo: https://leetcode.com/problems/word-break/solution/)

140. Word Break II

(Todo: https://leetcode.com/problems/word-break-ii/solution/)

81. Search in Rotated Sorted Array II

Solution	Date
Find Pivot	9/9

(Other Solutions, Reference: https://leetcode.com/problems/search-in-rotated-sorted-array-ii/discuss/28218/My-8ms-C++-solution-(o(logn)-on-average-o(n)-worst-case))

Solution	Date
One loop

44. Wildcard Matching

(Todo: https://leetcode.com/problems/wildcard-matching/discuss/17810/Linear-runtime-and-constant-space-solution)

(Todo: https://leetcode.com/problems/wildcard-matching/discuss/17957/C++-DP-solution)

Solution	Date
Dp

51. N-Queens

Solution	Date
Dfs	9/9

(Other Solutions, Reference: https://leetcode.com/problems/n-queens/discuss/19808/Accepted-4ms-c++-solution-use-backtracking-and-bitmask-easy-understand.)

Solution	Date
Bitmask

52. N-Queens II

(Other Solutions, Reference: https://leetcode.com/problems/n-queens-ii/discuss/20058/Accepted-Java-Solution?page=1)

Solution	Date
No place grid

79. Word Search

Solution	Date
Dfs	9/9

290. Word Pattern

Solution	Date
Two Map	9/10

80. Remove Duplicates from Sorted Array II

Solution	Date
Two Pointers	9/11

91. Decode Ways

Solution	Date
Dp	9/11

103. Binary Tree Zigzag Level Order Traversal

Solution	Date
Bfs	9/11
Recursive

150. Evaluate Reverse Polish Notation

Solution	Date
Stack	9/12
Recursive

647. Palindromic Substrings

Solution	Date
DP	9/13

74. Search a 2D Matrix

Solution	Date
Bin search	9/16
One Sorted	9/16
Row then Col	9/16

LintCode-38. Search a 2D Matrix II

Solution	Date
Row then Col	9/16

LintCode-609.TwoSum - Less than or equal to target

Solution	Date
Two Pointers	9/16

LintCode-587. Two Sum - Unique pairs

Solution	Date
Two Pointers	9/16

364. Nested List Weight Sum II

Solution	Date
Bfs	9/21

515. Find Largest Value in Each Tree Row

Solution	Date
Dfs	9/22

367. Valid Perfect Square

Solution	Date
Bin search	9/23

226. Invert Binary Tree

Solution	Date
Recursive	9/24
Iter

617. Merge Two Binary Trees

Solution	Date
Recursive	9/24
Iter

698. Partition to K Equal Sum Subsets

Solution	Date
Dfs	9/29
DP

199. Binary Tree Right Side View

Solution	Date
Bfs	10/13
Dfs	10/13

929. Unique Email Addresses (Go)

Solution	Date
	1/9

771. Jewels and Stones (Go)

Solution	Date
	1/9

760. Find Anagram Mappings (Go)

Solution	Date
	1/9

832. Flipping an Image (Go)

Solution	Date
	1/9

657. Robot Return to Origin (Go)

Solution	Date
	1/9

463. Island Perimeter (Go)

Solution	Date
DFS	1/9
Iterative	1/9