In this article, we’ll explore why LeetCode Hard Problems is an excellent resource for professionals with programming expertise.
Table of Contents
1. What Are LeetCode Easy Problems?
Leetcode Hard Problems are known for pushing the limits of problem-solving and programming skills. These questions challenge coding enthusiasts, professionals, and students alike, testing their ability to think critically and devise efficient algorithms.
While intimidating at first glance, mastering hard Leetcode questions can help you not only ace technical interviews but also sharpen your overall programming expertise.
2. Why Are Leetcode Hard Problems So Challenging?
Leetcode Hardest Problems often combine complex data structures, uncommon algorithms, and multi-layered edge cases. These questions require deep knowledge of dynamic programming, graph algorithms, and advanced recursion.
Examples of some hard Leetcode challenges include “N-Queens,” “Sliding Window Maximum,” and “Binary Tree Maximum Path Sum.”
They make you think outside the box, testing your analytical and debugging skills to the fullest.
3. Best Strategies to Solve Hard Leetcode Questions
- Break the Problem Into Steps: Begin by understanding the problem statement and constraints.
- Master Core Algorithms: Study common approaches like divide and conquer, DFS/BFS, and backtracking.
- Practice Regularly: Focus on a variety of hard Leetcode questions from different domains.
- Learn from Solutions: Reading optimal solutions after attempting a problem yourself can help you improve.
- Use Community Insights: Leetcode discussion forums often offer in-depth analyses and useful tips.
4. What Are Some of the Hardest Leetcode Problems?
Leetcode Hardest Problems to date include:
These challenges consistently appear in real-life software developer interviews.
List of all Leetcode Problem
1. Easy Problems
2. Medium Problems
3. Hard Problems
Hardest LeetCode Problems
| # | Problem | Level | Solution |
| 1 | Remove Invalid Parentheses | Hard | Link |
| 2 | Palindrome Pairs | Hard | Link |
| 3 | Word Ladder II | Hard | Link |
| 4 | Word Ladder | Hard | Link |
| 5 | Sliding Window Maximum | Hard | Link |
| 6 | Serialize and Deserialize Binary Tree | Hard | Link |
| 7 | Patching Array | Hard | Link |
| 8 | Longest Increasing Path in a Matrix | Hard | Link |
| 9 | Count of Range Sum | Hard | Link |
| 10 | Create Maximum Number | Hard | Link |
| 11 | Count of Smaller Numbers After Self | Hard | Link |
| 12 | Burst Balloons | Hard | Link |
| 13 | Find Median from Data Stream | Hard | Link |
| 14 | Basic Calculator | Hard | Link |
| 15 | Shortest Palindrome | Hard | Link |
| 16 | Maximum Sum of 3 Non Overlapping Subarrays | Hard | Link |
| 17 | Reconstruct Itinerary | Hard | Link |
| 18 | Decode Ways II | Hard | Link |
| 19 | Expression Add Operators | Hard | Link |
| 20 | Integer to English Words | Hard | Link |
| 21 | The Skyline Problem | Hard | Link |
| 22 | Word Break II | Hard | Link |
| 23 | Zuma Game | Hard | Link |
| 24 | Arithmetic Slices II Subsequence | Hard | Link |
| 25 | Split Array Largest Sum | Hard | Link |
| 26 | Binary Tree Maximum Path Sum | Hard | Link |
| 27 | Max Points on a Line | Hard | Link |
| 28 | Cut Off Trees for Golf Event | Hard | Link |
| 29 | Super Washing Machines | Hard | Link |
| 30 | LFU Cache | Hard | Link |
| 31 | Russian Doll Envelopes | Hard | Link |
| 32 | Max Sum of Rectangle No Larger Than K | Hard | Link |
| 33 | Perfect Rectangle | Hard | Link |
| 34 | Trapping Rain Water II | Hard | Link |
| 35 | Sliding Window Median | Hard | Link |
| 36 | Smallest Good Base | Hard | Link |
| 37 | Reverse Pairs | Hard | Link |
| 38 | Freedom Trail | Hard | Link |
| 39 | Student Attendance Record II | Hard | Link |
| 40 | Erect the Fence | Hard | Link |
| 41 | Kth Smallest Number in Multiplication Table | Hard | Link |
| 42 | 24 Game | Hard | Link |
| 43 | Redundant Connection II | Hard | Link |
| 44 | Find K-th Smallest Pair Distance | Hard | Link |
| 45 | Number of Atoms | Hard | Link |
| 46 | Best Time to Buy and Sell Stock III | Hard | Link |
| 47 | Count Different Palindromic Subsequences | Hard | Link |
| 48 | Dungeon Game | Hard | Link |
| 49 | Tag Validator | Hard | Link |
| 50 | Frog Jump | Hard | Link |
| 51 | All One Data Structure | Hard | Link |
| 52 | Falling Squares | Hard | Link |
| 53 | Largest Palindrome Product | Hard | Link |
| 54 | Insert Delete Get random O(1) Duplicates Allowed | Hard | Link |
| 55 | Find the Closest Palindrome | Hard | Link |
| 56 | Distinct Subsequences | Hard | Link |
| 57 | K-th Smallest in Lexicographical Order | Hard | Link |
| 58 | Palindrome Partitioning II | Hard | Link |
| 59 | Find Minimum in Rotated Sorted Array II | Hard | Link |
| 60 | Candy | Hard | Link |
| 61 | Best Time to Buy and Sell Stock IV | Hard | Link |
| 62 | Number of Digit One | Hard | Link |
| 63 | Self Crossing | Hard | Link |
| 64 | Data Stream as Disjoint Intervals | Hard | Link |
| 65 | Strong Password Checker | Hard | Link |
| 66 | Poor Pigs | Hard | Link |
| 67 | Count the Repetitions | Hard | Link |
| 68 | Concatenated Words | Hard | Link |
| 69 | IPO | Hard | Link |
| 70 | Remove Boxes | Hard | Link |
| 71 | Non Negative Integers without Consecutive Ones | Hard | Link |
| 72 | K-Inverse Pairs Array | Hard | Link |
| 73 | Course Schedule III | Hard | Link |
| 74 | Smallest Range Covering Elements from K Lists | Hard | Link |
| 75 | Strange Printer | Hard | Link |
| 76 | Stickers to Spell Word | Hard | Link |
| 77 | Random Pick with Blacklist | Hard | Link |
| 78 | Range Module | Hard | Link |
| 79 | Parse Lisp Expression | Hard | Link |
| 80 | My Calendar III | Hard | Link |
| 81 | Cherry Pickup | Hard | Link |
| 82 | Prefix and Suffix Search | Hard | Link |
| 83 | Cracking the Safe | Hard | Link |
| 84 | Contain Virus | Hard | Link |
| 85 | Set Intersection Size at least Two | Hard | Link |
| 86 | Couples Holding Hands | Hard | Link |
| 87 | Basic Calculator IV | Hard | Link |
| 88 | Sliding Puzzle | Hard | Link |
| 89 | Swim in Rising Water | Hard | Link |
| 90 | Reaching Points | Hard | Link |
| 91 | Transform to Chessboard | Hard | Link |
| 92 | Preimage Size of Factorial Zeroes Function | Hard | Link |
| 93 | Smallest Rotation with Highest Score | Hard | Link |
| 94 | Special Binary String | Hard | Link |
| 95 | Max Chunks to Make Sorted II | Hard | Link |
| 96 | Human Traffic of Stadium | Hard | Link |
| 97 | Department Top Three Salaries | Hard | Link |
| 98 | Trips and Users | Hard | Link |
| 99 | Number of Transactions Per Visit | Hard | Link |
| 100 | Report Contiguous Dates | Hard | Link |
| 101 | Valid Number | Hard | Link |
| 102 | Permutation Sequence | Hard | Link |
| 103 | N Queens II | Hard | Link |
| 104 | Minimum Window Substring | Hard | Link |
| 105 | Scramble String | Hard | Link |
| 106 | Maximal Rectangle | Hard | Link |
| 107 | N-Queens | Hard | Link |
| 108 | Wildcard Matching | Hard | Link |
| 109 | Trapping Rain Water | Hard | Link |
| 110 | First Missing Positive | Hard | Link |
| 111 | Longest Valid Parentheses | Hard | Link |
| 112 | Largest Rectangle in Histogram | Hard | Link |
| 113 | Sudoku Solver | Hard | Link |
| 114 | Substring with Concatenation of All Words | Hard | Link |
| 115 | Reverse Nodes in K-Group | Hard | Link |
| 116 | Regular Expression Matching | Hard | Link |
| 117 | Merge K-Sorted Lists | Hard | Link |
| 118 | Text Justification | Hard | Link |
| 119 | Contains Duplicate III | Hard | Link |
| 120 | Word Search II | Hard | Link |
| 121 | Maximum Sum of 3 Non-Overlapping Subarrays | Hard | Link |
FAQs
1. How Do I Approach Hard Leetcode Problems?
Start by solving simpler problems in the same category, followed by understanding algorithms and tackling the hard questions step by step.
2. Are Hard Leetcode Problems Necessary for Interviews?
Yes, for top-tier companies like Google, Meta, and Amazon, practicing hard Leetcode challenges is often essential.
3. Can I Improve Problem-Solving with Hard Leetcode Questions?
Absolutely! Solving these problems strengthens your analytical thinking, coding, and debugging skills.
4. How Long Does It Take to Master Hard Leetcode Questions?
Consistency is key. Dedicate a few months to consistent practice while gradually increasing difficulty levels.
Conclusion
Leetcode Hard Problems may seem insurmountable, but with persistence, strategy, and practice, they become less daunting. Tackling these challenges not only boosts your confidence for interviews but also transforms you into an exceptional problem solver.
Push your boundaries, keep challenging yourself, and watch your coding skills soar!
Happy Reading…