list-01

Question	Free?	Status	Difficulty	Topics	Similar Questions
1. Two Sum  🔗  📝	🆓	✅	⭐️	Array  🔗 Hash Table  🔗	15. 3Sum  🔗  📝 18. 4Sum  🔗  📝 167. Two Sum II - Input Array Is Sorted  🔗  📝 170. Two Sum III - Data structure design  🔗  📝 560. Subarray Sum Equals K  🔗  📝 653. Two Sum IV - Input is a BST  🔗  📝 1099. Two Sum Less Than K  🔗  📝 1679. Max Number of K-Sum Pairs  🔗  📝 1711. Count Good Meals  🔗  📝 2006. Count Number of Pairs With Absolute Difference K  🔗  📝 2023. Number of Pairs of Strings With Concatenation Equal to Target  🔗  📝 2200. Find All K-Distant Indices in an Array  🔗  📝 2351. First Letter to Appear Twice  🔗  📝 2354. Number of Excellent Pairs  🔗  📝 2367. Number of Arithmetic Triplets  🔗  📝
2. Add Two Numbers  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗 Math  🔗 Recursion  🔗	43. Multiply Strings  🔗  📝 67. Add Binary  🔗  📝 371. Sum of Two Integers  🔗  📝 415. Add Strings  🔗  📝 445. Add Two Numbers II  🔗  📝 989. Add to Array-Form of Integer  🔗  📝 1634. Add Two Polynomials Represented as Linked Lists  🔗  📝
3. Longest Substring Without Repeating Characters  🔗  📝	🆓	✅	⭐️⭐️	Hash Table  🔗 String  🔗 Sliding Window  🔗	159. Longest Substring with At Most Two Distinct Characters  🔗  📝 340. Longest Substring with At Most K Distinct Characters  🔗  📝 992. Subarrays with K Different Integers  🔗  📝 1695. Maximum Erasure Value  🔗  📝 2067. Number of Equal Count Substrings  🔗  📝 2260. Minimum Consecutive Cards to Pick Up  🔗  📝
4. Median of Two Sorted Arrays  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 Binary Search  🔗 Divide and Conquer  🔗
5. Longest Palindromic Substring  🔗  📝	🆓	✅	⭐️⭐️	String  🔗 Dynamic Programming  🔗	214. Shortest Palindrome  🔗  📝 266. Palindrome Permutation  🔗  📝 336. Palindrome Pairs  🔗  📝 516. Longest Palindromic Subsequence  🔗  📝 647. Palindromic Substrings  🔗  📝
6. Zigzag Conversion  🔗  📝	🆓	✅	⭐️⭐️	String  🔗
7. Reverse Integer  🔗  📝	🆓	✅	⭐️⭐️	Math  🔗	8. String to Integer (atoi)  🔗  📝 190. Reverse Bits  🔗  📝 2119. A Number After a Double Reversal  🔗  📝
8. String to Integer (atoi)  🔗  📝	🆓	✅	⭐️⭐️	String  🔗	7. Reverse Integer  🔗  📝 65. Valid Number  🔗  📝 2042. Check if Numbers Are Ascending in a Sentence  🔗  📝
9. Palindrome Number  🔗  📝	🆓	✅	⭐️	Math  🔗	234. Palindrome Linked List  🔗  📝 2217. Find Palindrome With Fixed Length  🔗  📝
10. Regular Expression Matching  🔗  📝	🆓		⭐️⭐️⭐️	String  🔗 Dynamic Programming  🔗 Recursion  🔗	44. Wildcard Matching  🔗  📝
11. Container With Most Water  🔗  📝	🆓	👀	⭐️⭐️	Array  🔗 Two Pointers  🔗 Greedy  🔗	42. Trapping Rain Water  🔗  📝
12. Integer to Roman  🔗  📝	🆓	✅	⭐️⭐️	Hash Table  🔗 Math  🔗 String  🔗	13. Roman to Integer  🔗  📝 273. Integer to English Words  🔗  📝
13. Roman to Integer  🔗  📝	🆓	✅	⭐️	Hash Table  🔗 Math  🔗 String  🔗	12. Integer to Roman  🔗  📝
14. Longest Common Prefix  🔗  📝	🆓	✅	⭐️	String  🔗
15. 3Sum  🔗  📝	🆓	👀	⭐️⭐️	Array  🔗 Two Pointers  🔗 Sorting  🔗	1. Two Sum  🔗  📝 16. 3Sum Closest  🔗  📝 18. 4Sum  🔗  📝 259. 3Sum Smaller  🔗  📝 2367. Number of Arithmetic Triplets  🔗  📝
16. 3Sum Closest  🔗  📝	🆓		⭐️⭐️	Array  🔗 Two Pointers  🔗 Sorting  🔗	15. 3Sum  🔗  📝 259. 3Sum Smaller  🔗  📝
17. Letter Combinations of a Phone Number  🔗  📝	🆓	✅	⭐️⭐️	Hash Table  🔗 String  🔗 Backtracking  🔗	22. Generate Parentheses  🔗  📝 39. Combination Sum  🔗  📝 401. Binary Watch  🔗  📝 2266. Count Number of Texts  🔗  📝
18. 4Sum  🔗  📝	🆓		⭐️⭐️	Array  🔗 Two Pointers  🔗 Sorting  🔗	1. Two Sum  🔗  📝 15. 3Sum  🔗  📝 454. 4Sum II  🔗  📝 1995. Count Special Quadruplets  🔗  📝
19. Remove Nth Node From End of List  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗 Two Pointers  🔗	1474. Delete N Nodes After M Nodes of a Linked List  🔗  📝 1721. Swapping Nodes in a Linked List  🔗  📝 2095. Delete the Middle Node of a Linked List  🔗  📝
20. Valid Parentheses  🔗  📝	🆓	✅	⭐️	String  🔗 Stack  🔗	22. Generate Parentheses  🔗  📝 32. Longest Valid Parentheses  🔗  📝 301. Remove Invalid Parentheses  🔗  📝 1003. Check If Word Is Valid After Substitutions  🔗  📝 2116. Check if a Parentheses String Can Be Valid  🔗  📝 2337. Move Pieces to Obtain a String  🔗  📝
21. Merge Two Sorted Lists  🔗  📝	🆓	✅	⭐️	Linked List  🔗 Recursion  🔗	23. Merge k Sorted Lists  🔗  📝 88. Merge Sorted Array  🔗  📝 148. Sort List  🔗  📝 244. Shortest Word Distance II  🔗  📝 1634. Add Two Polynomials Represented as Linked Lists  🔗  📝 1940. Longest Common Subsequence Between Sorted Arrays  🔗  📝
22. Generate Parentheses  🔗  📝	🆓	✅	⭐️⭐️	String  🔗 Dynamic Programming  🔗 Backtracking  🔗	17. Letter Combinations of a Phone Number  🔗  📝 20. Valid Parentheses  🔗  📝 2116. Check if a Parentheses String Can Be Valid  🔗  📝
23. Merge k Sorted Lists  🔗  📝	🆓	✅	⭐️⭐️⭐️	Linked List  🔗 Divide and Conquer  🔗 Heap (Priority Queue)  🔗 Merge Sort  🔗	21. Merge Two Sorted Lists  🔗  📝 264. Ugly Number II  🔗  📝
24. Swap Nodes in Pairs  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗 Recursion  🔗	25. Reverse Nodes in k-Group  🔗  📝 1721. Swapping Nodes in a Linked List  🔗  📝
25. Reverse Nodes in k-Group  🔗  📝	🆓	✅	⭐️⭐️⭐️	Linked List  🔗 Recursion  🔗	24. Swap Nodes in Pairs  🔗  📝 1721. Swapping Nodes in a Linked List  🔗  📝 2074. Reverse Nodes in Even Length Groups  🔗  📝
26. Remove Duplicates from Sorted Array  🔗  📝	🆓	✅	⭐️	Array  🔗 Two Pointers  🔗	27. Remove Element  🔗  📝 80. Remove Duplicates from Sorted Array II  🔗  📝
27. Remove Element  🔗  📝	🆓	✅	⭐️	Array  🔗 Two Pointers  🔗	26. Remove Duplicates from Sorted Array  🔗  📝 203. Remove Linked List Elements  🔗  📝 283. Move Zeroes  🔗  📝
28. Implement strStr()  🔗  📝	🆓	✅	⭐️	Two Pointers  🔗 String  🔗 String Matching  🔗	214. Shortest Palindrome  🔗  📝 459. Repeated Substring Pattern  🔗  📝
29. Divide Two Integers  🔗  📝	🆓	✅	⭐️⭐️	Math  🔗 Bit Manipulation  🔗
30. Substring with Concatenation of All Words  🔗  📝	🆓		⭐️⭐️⭐️	Hash Table  🔗 String  🔗 Sliding Window  🔗	76. Minimum Window Substring  🔗  📝
31. Next Permutation  🔗  📝	🆓		⭐️⭐️	Array  🔗 Two Pointers  🔗	46. Permutations  🔗  📝 47. Permutations II  🔗  📝 60. Permutation Sequence  🔗  📝 267. Palindrome Permutation II  🔗  📝 1850. Minimum Adjacent Swaps to Reach the Kth Smallest Number  🔗  📝
32. Longest Valid Parentheses  🔗  📝	🆓		⭐️⭐️⭐️	String  🔗 Dynamic Programming  🔗 Stack  🔗	20. Valid Parentheses  🔗  📝
33. Search in Rotated Sorted Array  🔗  📝	🆓		⭐️⭐️	Array  🔗 Binary Search  🔗	81. Search in Rotated Sorted Array II  🔗  📝 153. Find Minimum in Rotated Sorted Array  🔗  📝 2137. Pour Water Between Buckets to Make Water Levels Equal  🔗  📝
34. Find First and Last Position of Element in Sorted Array  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Binary Search  🔗	278. First Bad Version  🔗  📝 2055. Plates Between Candles  🔗  📝 2089. Find Target Indices After Sorting Array  🔗  📝
35. Search Insert Position  🔗  📝	🆓	✅	⭐️	Array  🔗 Binary Search  🔗	278. First Bad Version  🔗  📝
36. Valid Sudoku  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Hash Table  🔗 Matrix  🔗	37. Sudoku Solver  🔗  📝 2133. Check if Every Row and Column Contains All Numbers  🔗  📝
37. Sudoku Solver  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 Backtracking  🔗 Matrix  🔗	36. Valid Sudoku  🔗  📝 980. Unique Paths III  🔗  📝
38. Count and Say  🔗  📝	🆓		⭐️⭐️	String  🔗	271. Encode and Decode Strings  🔗  📝 443. String Compression  🔗  📝
39. Combination Sum  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗	17. Letter Combinations of a Phone Number  🔗  📝 40. Combination Sum II  🔗  📝 77. Combinations  🔗  📝 216. Combination Sum III  🔗  📝 254. Factor Combinations  🔗  📝 377. Combination Sum IV  🔗  📝
40. Combination Sum II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗	39. Combination Sum  🔗  📝
41. First Missing Positive  🔗  📝	🆓	✅	⭐️⭐️⭐️	Array  🔗 Hash Table  🔗	268. Missing Number  🔗  📝 287. Find the Duplicate Number  🔗  📝 448. Find All Numbers Disappeared in an Array  🔗  📝 765. Couples Holding Hands  🔗  📝 2336. Smallest Number in Infinite Set  🔗  📝
42. Trapping Rain Water  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 Two Pointers  🔗 Dynamic Programming  🔗 Stack  🔗 Monotonic Stack  🔗	11. Container With Most Water  🔗  📝 238. Product of Array Except Self  🔗  📝 407. Trapping Rain Water II  🔗  📝 755. Pour Water  🔗  📝
43. Multiply Strings  🔗  📝	🆓	👀	⭐️⭐️	Math  🔗 String  🔗 Simulation  🔗	2. Add Two Numbers  🔗  📝 66. Plus One  🔗  📝 67. Add Binary  🔗  📝 415. Add Strings  🔗  📝 2288. Apply Discount to Prices  🔗  📝
44. Wildcard Matching  🔗  📝	🆓		⭐️⭐️⭐️	String  🔗 Dynamic Programming  🔗 Greedy  🔗 Recursion  🔗	10. Regular Expression Matching  🔗  📝
45. Jump Game II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Dynamic Programming  🔗 Greedy  🔗	55. Jump Game  🔗  📝 1306. Jump Game III  🔗  📝 1871. Jump Game VII  🔗  📝 2297. Jump Game VIII  🔗  📝
46. Permutations  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗	31. Next Permutation  🔗  📝 47. Permutations II  🔗  📝 60. Permutation Sequence  🔗  📝 77. Combinations  🔗  📝
47. Permutations II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗	31. Next Permutation  🔗  📝 46. Permutations  🔗  📝 267. Palindrome Permutation II  🔗  📝 996. Number of Squareful Arrays  🔗  📝
48. Rotate Image  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Math  🔗 Matrix  🔗	1886. Determine Whether Matrix Can Be Obtained By Rotation  🔗  📝
49. Group Anagrams  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Hash Table  🔗 String  🔗 Sorting  🔗	242. Valid Anagram  🔗  📝 249. Group Shifted Strings  🔗  📝 2273. Find Resultant Array After Removing Anagrams  🔗  📝
50. Pow(x, n)  🔗  📝	🆓	✅	⭐️⭐️	Math  🔗 Recursion  🔗	69. Sqrt(x)  🔗  📝 372. Super Pow  🔗  📝
51. N-Queens  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 Backtracking  🔗	52. N-Queens II  🔗  📝 1001. Grid Illumination  🔗  📝
52. N-Queens II  🔗  📝	🆓		⭐️⭐️⭐️	Backtracking  🔗	51. N-Queens  🔗  📝
53. Maximum Subarray  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Divide and Conquer  🔗 Dynamic Programming  🔗	121. Best Time to Buy and Sell Stock  🔗  📝 152. Maximum Product Subarray  🔗  📝 697. Degree of an Array  🔗  📝 978. Longest Turbulent Subarray  🔗  📝 1746. Maximum Subarray Sum After One Operation  🔗  📝 1749. Maximum Absolute Sum of Any Subarray  🔗  📝 2272. Substring With Largest Variance  🔗  📝 2302. Count Subarrays With Score Less Than K  🔗  📝 2321. Maximum Score Of Spliced Array  🔗  📝
54. Spiral Matrix  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Matrix  🔗 Simulation  🔗	59. Spiral Matrix II  🔗  📝 885. Spiral Matrix III  🔗  📝 2326. Spiral Matrix IV  🔗  📝
55. Jump Game  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Dynamic Programming  🔗 Greedy  🔗	45. Jump Game II  🔗  📝 1306. Jump Game III  🔗  📝 1871. Jump Game VII  🔗  📝 2297. Jump Game VIII  🔗  📝
56. Merge Intervals  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Sorting  🔗	57. Insert Interval  🔗  📝 252. Meeting Rooms  🔗  📝 253. Meeting Rooms II  🔗  📝 495. Teemo Attacking  🔗  📝 616. Add Bold Tag in String  🔗  📝 715. Range Module  🔗  📝 759. Employee Free Time  🔗  📝 763. Partition Labels  🔗  📝 986. Interval List Intersections  🔗  📝 2158. Amount of New Area Painted Each Day  🔗  📝 2213. Longest Substring of One Repeating Character  🔗  📝 2276. Count Integers in Intervals  🔗  📝
57. Insert Interval  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗	56. Merge Intervals  🔗  📝 715. Range Module  🔗  📝 2276. Count Integers in Intervals  🔗  📝
58. Length of Last Word  🔗  📝	🆓	✅	⭐️	String  🔗
59. Spiral Matrix II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Matrix  🔗 Simulation  🔗	54. Spiral Matrix  🔗  📝 885. Spiral Matrix III  🔗  📝 2326. Spiral Matrix IV  🔗  📝
60. Permutation Sequence  🔗  📝	🆓	✅	⭐️⭐️⭐️	Math  🔗 Recursion  🔗	31. Next Permutation  🔗  📝 46. Permutations  🔗  📝
61. Rotate List  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗 Two Pointers  🔗	189. Rotate Array  🔗  📝 725. Split Linked List in Parts  🔗  📝
62. Unique Paths  🔗  📝	🆓	✅	⭐️⭐️	Math  🔗 Dynamic Programming  🔗 Combinatorics  🔗	63. Unique Paths II  🔗  📝 64. Minimum Path Sum  🔗  📝 174. Dungeon Game  🔗  📝 2087. Minimum Cost Homecoming of a Robot in a Grid  🔗  📝 2304. Minimum Path Cost in a Grid  🔗  📝
63. Unique Paths II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Dynamic Programming  🔗 Matrix  🔗	62. Unique Paths  🔗  📝 980. Unique Paths III  🔗  📝 2304. Minimum Path Cost in a Grid  🔗  📝
64. Minimum Path Sum  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Dynamic Programming  🔗 Matrix  🔗	62. Unique Paths  🔗  📝 174. Dungeon Game  🔗  📝 741. Cherry Pickup  🔗  📝 1937. Maximum Number of Points with Cost  🔗  📝 2087. Minimum Cost Homecoming of a Robot in a Grid  🔗  📝 2304. Minimum Path Cost in a Grid  🔗  📝
65. Valid Number  🔗  📝	🆓		⭐️⭐️⭐️	String  🔗	8. String to Integer (atoi)  🔗  📝
66. Plus One  🔗  📝	🆓	✅	⭐️	Array  🔗 Math  🔗	43. Multiply Strings  🔗  📝 67. Add Binary  🔗  📝 369. Plus One Linked List  🔗  📝 989. Add to Array-Form of Integer  🔗  📝
67. Add Binary  🔗  📝	🆓	✅	⭐️	Math  🔗 String  🔗 Bit Manipulation  🔗 Simulation  🔗	2. Add Two Numbers  🔗  📝 43. Multiply Strings  🔗  📝 66. Plus One  🔗  📝 989. Add to Array-Form of Integer  🔗  📝
68. Text Justification  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 String  🔗 Simulation  🔗	1592. Rearrange Spaces Between Words  🔗  📝 2138. Divide a String Into Groups of Size k  🔗  📝
69. Sqrt(x)  🔗  📝	🆓	✅	⭐️	Math  🔗 Binary Search  🔗	50. Pow(x, n)  🔗  📝 367. Valid Perfect Square  🔗  📝
70. Climbing Stairs  🔗  📝	🆓	✅	⭐️	Math  🔗 Dynamic Programming  🔗 Memoization  🔗	509. Fibonacci Number  🔗  📝 746. Min Cost Climbing Stairs  🔗  📝 1137. N-th Tribonacci Number  🔗  📝 2244. Minimum Rounds to Complete All Tasks  🔗  📝 2320. Count Number of Ways to Place Houses  🔗  📝
71. Simplify Path  🔗  📝	🆓	✅	⭐️⭐️	String  🔗 Stack  🔗
72. Edit Distance  🔗  📝	🆓		⭐️⭐️⭐️	String  🔗 Dynamic Programming  🔗	161. One Edit Distance  🔗  📝 583. Delete Operation for Two Strings  🔗  📝 712. Minimum ASCII Delete Sum for Two Strings  🔗  📝 1035. Uncrossed Lines  🔗  📝 2209. Minimum White Tiles After Covering With Carpets  🔗  📝
73. Set Matrix Zeroes  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Hash Table  🔗 Matrix  🔗	289. Game of Life  🔗  📝 2123. Minimum Operations to Remove Adjacent Ones in Matrix  🔗  📝 2125. Number of Laser Beams in a Bank  🔗  📝 2174. Remove All Ones With Row and Column Flips II  🔗  📝
74. Search a 2D Matrix  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Binary Search  🔗 Matrix  🔗	240. Search a 2D Matrix II  🔗  📝
75. Sort Colors  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Two Pointers  🔗 Sorting  🔗	148. Sort List  🔗  📝 280. Wiggle Sort  🔗  📝 324. Wiggle Sort II  🔗  📝
76. Minimum Window Substring  🔗  📝	🆓		⭐️⭐️⭐️	Hash Table  🔗 String  🔗 Sliding Window  🔗	30. Substring with Concatenation of All Words  🔗  📝 209. Minimum Size Subarray Sum  🔗  📝 239. Sliding Window Maximum  🔗  📝 567. Permutation in String  🔗  📝 632. Smallest Range Covering Elements from K Lists  🔗  📝 727. Minimum Window Subsequence  🔗  📝
77. Combinations  🔗  📝	🆓		⭐️⭐️	Backtracking  🔗	39. Combination Sum  🔗  📝 46. Permutations  🔗  📝
78. Subsets  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗 Bit Manipulation  🔗	90. Subsets II  🔗  📝 320. Generalized Abbreviation  🔗  📝 784. Letter Case Permutation  🔗  📝 1982. Find Array Given Subset Sums  🔗  📝 2044. Count Number of Maximum Bitwise-OR Subsets  🔗  📝
79. Word Search  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗 Matrix  🔗	212. Word Search II  🔗  📝
80. Remove Duplicates from Sorted Array II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Two Pointers  🔗	26. Remove Duplicates from Sorted Array  🔗  📝
81. Search in Rotated Sorted Array II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Binary Search  🔗	33. Search in Rotated Sorted Array  🔗  📝
82. Remove Duplicates from Sorted List II  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗 Two Pointers  🔗	83. Remove Duplicates from Sorted List  🔗  📝 1836. Remove Duplicates From an Unsorted Linked List  🔗  📝
83. Remove Duplicates from Sorted List  🔗  📝	🆓	✅	⭐️	Linked List  🔗	82. Remove Duplicates from Sorted List II  🔗  📝 1836. Remove Duplicates From an Unsorted Linked List  🔗  📝
84. Largest Rectangle in Histogram  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 Stack  🔗 Monotonic Stack  🔗	85. Maximal Rectangle  🔗  📝 1793. Maximum Score of a Good Subarray  🔗  📝
85. Maximal Rectangle  🔗  📝	🆓		⭐️⭐️⭐️	Array  🔗 Dynamic Programming  🔗 Stack  🔗 Matrix  🔗 Monotonic Stack  🔗	84. Largest Rectangle in Histogram  🔗  📝 221. Maximal Square  🔗  📝
86. Partition List  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗 Two Pointers  🔗	2161. Partition Array According to Given Pivot  🔗  📝
87. Scramble String  🔗  📝	🆓		⭐️⭐️⭐️	String  🔗 Dynamic Programming  🔗
88. Merge Sorted Array  🔗  📝	🆓	✅	⭐️	Array  🔗 Two Pointers  🔗 Sorting  🔗	21. Merge Two Sorted Lists  🔗  📝 977. Squares of a Sorted Array  🔗  📝 986. Interval List Intersections  🔗  📝
89. Gray Code  🔗  📝	🆓	✅	⭐️⭐️	Math  🔗 Backtracking  🔗 Bit Manipulation  🔗	717. 1-bit and 2-bit Characters  🔗  📝
90. Subsets II  🔗  📝	🆓	✅	⭐️⭐️	Array  🔗 Backtracking  🔗 Bit Manipulation  🔗	78. Subsets  🔗  📝 1982. Find Array Given Subset Sums  🔗  📝
91. Decode Ways  🔗  📝	🆓		⭐️⭐️	String  🔗 Dynamic Programming  🔗	639. Decode Ways II  🔗  📝 1977. Number of Ways to Separate Numbers  🔗  📝 2266. Count Number of Texts  🔗  📝
92. Reverse Linked List II  🔗  📝	🆓	✅	⭐️⭐️	Linked List  🔗	206. Reverse Linked List  🔗  📝
93. Restore IP Addresses  🔗  📝	🆓	✅	⭐️⭐️	String  🔗 Backtracking  🔗	751. IP to CIDR  🔗  📝
94. Binary Tree Inorder Traversal  🔗  📝	🆓	✅	⭐️	Stack  🔗 Tree  🔗 Depth-First Search  🔗 Binary Tree  🔗	98. Validate Binary Search Tree  🔗  📝 144. Binary Tree Preorder Traversal  🔗  📝 145. Binary Tree Postorder Traversal  🔗  📝 173. Binary Search Tree Iterator  🔗  📝 230. Kth Smallest Element in a BST  🔗  📝 272. Closest Binary Search Tree Value II  🔗  📝 285. Inorder Successor in BST  🔗  📝 426. Convert Binary Search Tree to Sorted Doubly Linked List  🔗  📝 783. Minimum Distance Between BST Nodes  🔗  📝
95. Unique Binary Search Trees II  🔗  📝	🆓		⭐️⭐️	Dynamic Programming  🔗 Backtracking  🔗 Tree  🔗 Binary Search Tree  🔗 Binary Tree  🔗	96. Unique Binary Search Trees  🔗  📝 241. Different Ways to Add Parentheses  🔗  📝
96. Unique Binary Search Trees  🔗  📝	🆓	✅	⭐️⭐️	Math  🔗 Dynamic Programming  🔗 Tree  🔗 Binary Search Tree  🔗 Binary Tree  🔗	95. Unique Binary Search Trees II  🔗  📝
97. Interleaving String  🔗  📝	🆓	👀	⭐️⭐️	String  🔗 Dynamic Programming  🔗
98. Validate Binary Search Tree  🔗  📝	🆓	✅	⭐️⭐️	Tree  🔗 Depth-First Search  🔗 Binary Search Tree  🔗 Binary Tree  🔗	94. Binary Tree Inorder Traversal  🔗  📝 501. Find Mode in Binary Search Tree  🔗  📝
99. Recover Binary Search Tree  🔗  📝	🆓	✅	⭐️⭐️	Tree  🔗 Depth-First Search  🔗 Binary Search Tree  🔗 Binary Tree  🔗
100. Same Tree  🔗  📝	🆓	✅	⭐️	Tree  🔗 Depth-First Search  🔗 Breadth-First Search  🔗 Binary Tree  🔗