LeetCode Interview Prep
Progress¶
Lessons learned¶
- 2026-04-07
- read carefully the questions and conditions
- find the solution on paper. if you don't have it on paper, odds are you're not going to have it on computer.
- when you find the trick, solution are often simple and classic.
- 2026-04-11
- draw
- try different visual representations
- it helps see and find patterns
- it helps think about the right data structures to use
- run algorithm by hand with visuals using small values
- re-state/reformulate the problem
- draw
- 2026-04-14
- When your test fail, maybe some test cases are wrong and your implementation of the solution is right.
- Be sure the helper you use in your test to build data structures like list, trees, ... are correct. Your tests may be failing because of them being wrong.
- 2026-04-15
- When your reasoning on a "set" of something (can be tuple, list,
set, tree, ...), change the way you look at it. You can look at
its elements individualy or see them as subsets. For instance,
if
x = [1, 2, 3, 4, 5], you can look at1, or any other of its elements, or, like thisx = [A | B]whereA = [1, 2]andB = [3, 4, 5].
- When your reasoning on a "set" of something (can be tuple, list,
set, tree, ...), change the way you look at it. You can look at
its elements individualy or see them as subsets. For instance,
if
- 2026-04-19
- Sometimes the solution (specifically for time and space constraints) uses a property about the system or a specific algorithm you never encounter before. Chances are you wont find it in a limited time. It's ok, don't take it personally. After trying your best, just learn the trick and add it in your toolkit.
LeetCode Top Easy¶
[25/48] LeetCode Top Easy
- ——— Array ———
- 26. Remove Duplicates from Sorted Array
- 122. Best Time to Buy and Sell Stock II
- 189. Rotate Array
- 217. Contains Duplicate
- 136. Single Number
- 350. Intersection of Two Arrays II
- 66. Plus One
- 283. Move Zeroes
- 1. Two Sum
- 36. Valid Sudoku
- 48. Rotate Image
- ——— Strings ———
- 344. Reverse String
- 7. Reverse Integer
- 387. First Unique Character in a String
- 242. Valid Anagram
- 125. Valid Palindrome
- 8. String to Integer (atoi)
- 28. Find the Index of the First Occurrence in a String
- 14. Longest Common Prefix
- ——— Linked List ———
- 237. Delete Node in a Linked List
- 19. Remove Nth Node From End of List
- 206. Reverse Linked List
- 21. Merge Two Sorted Lists
- 234. Palindrome Linked List
- 141. Linked List Cycle
- ——— Trees ———
- 104. Maximum Depth of Binary Tree
- 98. Validate Binary Search Tree
- 101. Symmetric Tree
- 102. Binary Tree Level Order Traversal
- 108. Convert Sorted Array to Binary Search Tree
- ——— Sorting and Searching ———
- 88. Merge Sorted Array
- 278. First Bad Version
- ——— Dynamic Programming ———
- 70. Climbing Stairs
- 121. Best Time to Buy and Sell Stock
- 53. Maximum Subarray
- 198. House Robber
- ——— Design ———
- 384. Shuffle an Array
- 155. Min Stack
- ——— Math ———
- 412. Fizz Buzz
- 204. Count Primes
- 326. Power of Three
- 13. Roman to Integer
- ——— Others ———
- 191. Number of Bits
- 461. Hamming Distance
- 190. Reverse Bits
- 118. Pascal's Triangle
- 20. Valid Parentheses
- 268. Missing Number
LeetCode SQL 50¶
[0/50] LeetCode SQL 50
- ——— Select ———
- 1757. Recyclable and Low Fat Products
- 584. Find Customer Referee
- 595. Big Countries
- 1148. Article Views I
- 1683. Invalid Tweets
- ——— Basic Joins ———
- 1378. Replace Employee ID With The Unique Identifier
- 1068. Product Sales Analysis I
- 1581. Customer Who Visited but Did Not Make Any Transactions
- 197. Rising Temperature
- 1661. Average Time of Process per Machine
- 577. Employee Bonus
- 1280. Students and Examinations
- 570. Managers with at Least 5 Direct Reports
- 1934. Confirmation Rate
- ——— Basic Aggregate Functions ———
- 620. Not Boring Movies
- 1251. Average Selling Price
- 1075. Project Employees I
- 1633. Percentage of Users Attended a Contest
- 1211. Queries Quality and Percentage
- 1193. Monthly Transactions I
- 1174. Immediate Food Delivery II
- 550. Game Play Analysis IV
- ——— Sorting and Grouping ———
- 2356. Number of Unique Subjects Taught by Each Teacher
- 1141. User Activity for the Past 30 Days I
- 1070. Product Sales Analysis III
- 596. Classes With at Least 5 Students
- 1729. Find Followers Count
- 619. Biggest Single Number
- 1045. Customers Who Bought All Products
- ——— Advanced Select and Joins ———
- 1731. The Number of Employees Which Report to Each Employee
- 1789. Primary Department for Each Employee
- 610. Triangle Judgement
- 180. Consecutive Numbers
- 1164. Product Price at a Given Date
- 1204. Last Person to Fit in the Bus
- 1907. Count Salary Categories
- ——— Subqueries ———
- 1978. Employees Whose Manager Left the Company
- 626. Exchange Seats
- 1341. Movie Rating
- 1321. Restaurant Growth
- 602. Friend Requests II: Who Has the Most Friends
- 585. Investments in 2016
- 185. Department Top Three Salaries
- ——— Advanced String Functions / Regex / Clause ———
- 1667. Fix Names in a Table
- 1527. Patients With a Condition
- 196. Delete Duplicate Emails
- 176. Second Highest Salary
- 1484. Group Sold Products By The Date
- 1327. List the Products Ordered in a Period
- 1517. Find Users With Valid E-Mails