Popular Problems

Easy

1. Design Parking System (87.1%)
2. Make Array Zero by Subtracting Equal Amounts (73.3%)
3. Maximum Units on a Truck (74.3%)

Medium

1. LRU Cache (45.2%)
2. Number of Islands (62.3%)
3. Reorganize String (56.2%)
4. Meeting Rooms II (52.1%)
5. Group Anagrams (70.9%)
6. Analyze User Website Visit Pattern (43.7%)
7. Minimum Health to Beat Game (58.7%)
8. Design Tic-Tac-Toe (58.6%)
9. Copy List with Random Pointer (60.5%)
10. Rotting Oranges (56.6%)
11. Course Schedule (49.2%)
12. Search Suggestions System (65.0%)
13. K Closest Points to Origin (67.9%)
14. All Nodes Distance K in Binary Tree (66.4%)
15. Plates Between Candles (46.6%)
16. Find Triangular Sum of an Array (78.8%)
17. Number of Ways to Select Buildings (50.5%)
18. Sequential Digits (65.3%)
19. Maximum Length of Subarray With Positive Product (44.4%)
20. Find Good Days to Rob the Bank (50.4%)
21. Reorder Data in Log Files (56.8%)
22. Minimum Adjacent Swaps to Make a Valid Array (72.2%)
23. Sum of Subarray Ranges (60.1%)
24. Minimum Number of Swaps to Make the Binary String Alternating (43.4%)
25. Design an Expression Tree With Evaluate Function (82.4%)
26. Minimum Number of Keypresses (71.3%)

Hard

1. Trapping Rain Water (65.1%)
2. Integer to English Words (34.4%)
3. Word Ladder (42.8%)
4. Design In-Memory File System (48.2%)
5. Find Median from Data Stream (53.3%)
6. Sliding Window Maximum (47.6%)
7. Word Break II (53.6%)
8. Minimum Number of Moves to Make Palindrome (52.0%)
9. Concatenated Words (49.4%)
10. Maximum Number of Books You Can Take (39.3%)
11. Find the K-Sum of an Array (39.6%)
12. Race Car (44.1%)
13. Sum of Total Strength of Wizards (28.3%)
14. Find K-th Smallest Pair Distance (45.8%)
15. Count Unique Characters of All Substrings of a Given String (52.9%)
16. Substring With Largest Variance (45.9%)
17. Total Appeal of A String (55.8%)
18. Build Binary Expression Tree From Infix Expression (62.5%)
19. Sequentially Ordinal Rank Tracker (61.7%)
20. Maximum Number of Robots Within Budget (36.8%)

Additional Categories

• Design Problems:
• 146. LRU Cache

1. Design Tic-Tac-Toe
2. Design Parking System
3. Design In-Memory File System
4. Design an Expression Tree

• Tree/Graph Problems:
• 200. Number of Islands

1. All Nodes Distance K in Binary Tree
2. Boundary of Binary Tree
3. Word Ladder (BFS)

• String Manipulation:
• 767. Reorganize String

1. Group Anagrams
2. Minimum Moves to Make Palindrome
3. Substring With Largest Variance

• Dynamic Programming / Sliding Window:
• 42. Trapping Rain Water

1. Sliding Window Maximum
2. Word Break II
3. Maximum Length of Subarray With Positive Product

• Heap / Priority Queue:
• 253. Meeting Rooms II

1. Find Median from Data Stream
2. K Closest Points to Origin

Would you like a deeper breakdown of any specific problem or category?