18 4Sum / Medium

57 Insert Interval / Hard

31. Next Permutation

352 Data Stream as Disjoint Intervals / Hard

128 Longest Consecutive Sequence / Hard

81 Search in Rotated Sorted Array II / Medium

324 Wiggle Sort II / Medium

164 Maximum Gap / Hard

334 Increasing Triplet Subsequence / Medium

42 Trapping Rain Water / Hard

84 Largest Rectangle in Histogram / Hard

85 Maximal Rectangle / Hard

287 Find the Duplicate Number / Medium

239 Sliding Window Maximum / Hard

295 Find Median from Data Stream / Hard

48 Rotate Image / Medium

85 Maximal Rectangle / Hard

37 Sudoku Solver / Hard

63 Unique Paths II / Medium (dynamic programming)

219. Contains Duplicate II

381Insert Delete GetRandom O(1) - Duplicates allowed / Hard

215 Kth Largest Element in an Array Medium

347 Top K Frequent Elements / Medium

41 First Missing Positive / Hard

37 Sudoku Solver / Hard

105 Construct Binary Tree from Preorder and Inorder Traversal / Medium

106 Construct Binary Tree from Inorder and Postorder Traversal / Medium

595 Big Countries / Easy SELECT, WHERE

620 Not Boring Movies / Easy ORDER

178 Rank Scores / Medium COUNT, DISTINCT, SELECT

175 Combine Two Tables / Easy LEFT JOIN

181 Employees Earning More Than Their Managers / Easy JOIN, SELECT

183 Customers Who Never Order / Easy JOIN, SELECT

197 Rising Temperature / Easy DATEDIFF

601 Human Traffic of Stadium / Hard DISTINCT, SELECT, 3 TABLES JOIN

180 Consecutive Numbers / Medium DISTINCT, SELECT, 3 TABLES JOIN

184 Department Highest Salary / Medium WHERE, IN, MAX, GROUP BY

185 Department Top Three Salaries / Hard COUNT, JOIN

262 Trips and Users SUM, COUNT, CASE, GROUP BY

176 Second Highest Salary / EasyLIMIT, OFFSET, IFNULL

177 Nth Highest Salary / Medium CREATE FUNCTION, DECLARE, SET, LIMIT, OFFSET

182 Duplicate Emails / Easy GROUP BY, HAVING, COUNT

596 Classes More Than 5 Students / Easy DISTINCT, GROUP BY, HAVING, COUNT

184 Department Highest Salary / Medium WHERE, IN, MAX, GROUP BY

262 Trips and Users SUM, COUNT, CASE, GROUP BY

196 Delete Duplicate Emails / Easy DELETE

627 Swap Salary / Easy UPDATE, SET, IF

627 Swap Salary / Easy UPDATE, SET, IF

626 Exchange Seats / Medium CASE, COUNT

178 Rank Scores / Medium COUNT, DISTINCT, SELECT

185 Department Top Three Salaries / Hard COUNT, JOIN

262 Trips and Users SUM, COUNT, CASE, GROUP BY

177 Nth Highest Salary / Medium CREATE FUNCTION, DECLARE, SET, LIMIT, OFFSET