Leetcode: Google tagged | Hard level algorithms | Last six months | 55 algorithm problems

Hard level - 55 algorithms to work on 

1284	Minimum Number of Flips to Convert Binary Matrix to Zero Matrix

1944	Number of Visible People in a Queue

428	Serialize and Deserialize N-ary Tree

1096	Brace Expansion II

847	Shortest Path Visiting All Nodes

1597	Build Binary Expression Tree From Infix Expression

2158	Amount of New Area Painted Each Day

296	Best Meeting Point

1948	Delete Duplicate Folders in System

778	Swim in Rising Water

632	Smallest Range Covering Elements from K Lists

302	Smallest Rectangle Enclosing Black Pixels

272	Closest Binary Search Tree Value II

753	Cracking the Safe

1240	Tiling a Rectangle with the Fewest Squares

425	Word Squares

410	Split Array Largest Sum

1793	Maximum Score of a Good Subarray

1235	Maximum Profit in Job Scheduling

920	Number of Music Playlists

465	Optimal Account Balancing

679

24 Game

1263	Minimum Moves to Move a Box to Their Target Location

588	Design In-Memory File System

642	Design Search Autocomplete System

772	Basic Calculator III

407	Trapping Rain Water II

1499	Max Value of Equation

499	The Maze III

815	Bus Routes

1345	Jump Game IV

818

Race Car

727	Minimum Window Subsequence

843	Guess the Word

631	Design Excel Sum Formula

60	Permutation Sequence

315	Count of Smaller Numbers After Self

1397	Find All Good Strings

1606	Find Servers That Handled Most Number of Requests

2188	Minimum Time to Finish the Race

224	Basic Calculator

460

LFU Cache

354	Russian Doll Envelopes

358	Rearrange String k Distance Apart

1610	Maximum Number of Visible Points

871	Minimum Number of Refueling Stops

68	Text Justification

269	Alien Dictionary

803	Bricks Falling When Hit

2092	Find All People With Secret

2242	Maximum Score of a Node Sequence

2132	Stamping the Grid

564	Find the Closest Palindrome

420	Strong Password Checker