Curated Problem Set
Conquer Searching Problems
Master fundamental data structures and algorithms. Track your progress, solve curated problems, and prepare for your next big technical interview.
CPBrains Ultimate DSA Sheet
This sheet is designed for beginners who are starting their DSA journey and want to build a strong foundation. It covers all essential topics with a carefully curated set of problems to help you learn, practice, and master concepts effectively.
How to use: Start by solving the first 8–10 problems from each topic to understand the basics and build intuition.
Once you complete all topics, revisit them and solve the remaining problems to strengthen your understanding and gain confidence. 🚀
Problem Directory
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Sqrt(x) | Easy | Solve |
| 2 | Climbing Stairs | Easy | Solve |
| 3 | Add Digits | Easy | Solve |
| 4 | Happy Number | Easy | Solve |
| 5 | Ugly Number | Easy | Solve |
| 6 | Perfect Number | Easy | Solve |
| 7 | Reverse Integer | Easy | Solve |
| 8 | Palindrome Number | Easy | Solve |
| 9 | Power of Three | Easy | Solve |
| 10 | Power of Four | Easy | Solve |
| 11 | Excel Sheet Column Number | Easy | Solve |
| 12 | Excel Sheet Column Title | Easy | Solve |
| 13 | Valid Boomerang | Easy | Solve |
| 14 | Find the Winner of the Circular Game | Easy | Solve |
| 15 | Base 7 | Easy | Solve |
| 16 | Divide Two Integers | Medium | Solve |
| 17 | Count Primes | Medium | Solve |
| 18 | Integer Break | Medium | Solve |
| 19 | Pow(x, n) | Medium | Solve |
| 20 | Multiply Strings | Medium | Solve |
| 21 | Fraction to Recurring Decimal | Medium | Solve |
| 22 | Rotate Function | Medium | Solve |
| 23 | Valid Square | Medium | Solve |
| 24 | Complex Number Multiplication | Medium | Solve |
| 25 | Random Pick with Weight | Medium | Solve |
| 26 | Max Points on a Line | Hard | Solve |
| 27 | Basic Calculator | Hard | Solve |
| 28 | Number of Digit One | Hard | Solve |
| 29 | Kth Smallest Number in Multiplication Table | Hard | Solve |
| 30 | Erect the Fence | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Number of 1 Bits | Easy | Solve |
| 2 | Counting Bits | Easy | Solve |
| 3 | Reverse Bits | Easy | Solve |
| 4 | Power of Two | Easy | Solve |
| 5 | Single Number | Easy | Solve |
| 6 | Missing Number | Easy | Solve |
| 7 | Hamming Distance | Easy | Solve |
| 8 | Binary Watch | Easy | Solve |
| 9 | Set Mismatch | Easy | Solve |
| 10 | Alternating Bits | Easy | Solve |
| 11 | Prime Number of Set Bits in Binary Representation | Easy | Solve |
| 12 | Sort Integers by The Number of 1 Bits | Easy | Solve |
| 13 | XOR Operation in an Array | Easy | Solve |
| 14 | Decode XORed Array | Easy | Solve |
| 15 | Minimum Bit Flips to Convert Number | Easy | Solve |
| 16 | Single Number II | Medium | Solve |
| 17 | Single Number III | Medium | Solve |
| 18 | Bitwise AND of Numbers Range | Medium | Solve |
| 19 | Maximum Product of Word Lengths | Medium | Solve |
| 20 | Subsets | Medium | Solve |
| 21 | Gray Code | Medium | Solve |
| 22 | Total Hamming Distance | Medium | Solve |
| 23 | Minimum Flips to Make a OR b Equal to c | Medium | Solve |
| 24 | Find the Original Array of Prefix Xor | Medium | Solve |
| 25 | Neighboring Bitwise XOR | Medium | Solve |
| 26 | Maximum XOR of Two Numbers in an Array | Hard | Solve |
| 27 | Maximum XOR With an Element From Array | Hard | Solve |
| 28 | Find Minimum Time to Finish All Jobs | Hard | Solve |
| 29 | Maximum Score Words Formed by Letters | Hard | Solve |
| 30 | Minimum One Bit Operations to Make Integers Zero | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Fibonacci Number | Easy | Solve |
| 2 | N-th Tribonacci Number | Easy | Solve |
| 3 | Power of Two | Easy | Solve |
| 4 | Power of Three | Easy | Solve |
| 5 | Power of Four | Easy | Solve |
| 6 | Reverse String | Easy | Solve |
| 7 | Reverse Linked List | Easy | Solve |
| 8 | Merge Two Sorted Lists | Easy | Solve |
| 9 | Symmetric Tree | Easy | Solve |
| 10 | Maximum Depth of Binary Tree | Easy | Solve |
| 11 | Invert Binary Tree | Easy | Solve |
| 12 | Search in a Binary Search Tree | Easy | Solve |
| 13 | Path Sum | Easy | Solve |
| 14 | Range Sum of BST | Easy | Solve |
| 15 | Minimum Distance Between BST Nodes | Easy | Solve |
| 16 | Pow(x, n) | Medium | Solve |
| 17 | Swap Nodes in Pairs | Medium | Solve |
| 18 | Add Two Numbers | Medium | Solve |
| 19 | K-th Symbol in Grammar | Medium | Solve |
| 20 | Different Ways to Add Parentheses | Medium | Solve |
| 21 | Elimination Game | Medium | Solve |
| 22 | Predict the Winner | Medium | Solve |
| 23 | Decode String | Medium | Solve |
| 24 | Find the Winner of the Circular Game | Medium | Solve |
| 25 | Construct Quad Tree | Medium | Solve |
| 26 | Basic Calculator | Hard | Solve |
| 27 | Integer to English Words | Hard | Solve |
| 28 | Parse Lisp Expression | Hard | Solve |
| 29 | Stamping The Sequence | Hard | Solve |
| 30 | K-th Smallest in Lexicographical Order | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Contains Duplicate | Easy | Solve |
| 2 | Valid Anagram | Easy | Solve |
| 3 | Majority Element | Easy | Solve |
| 4 | Missing Number | Easy | Solve |
| 5 | Intersection of Two Arrays | Easy | Solve |
| 6 | Squares of a Sorted Array | Easy | Solve |
| 7 | Assign Cookies | Easy | Solve |
| 8 | Array Partition | Easy | Solve |
| 9 | Maximum Product of Three Numbers | Easy | Solve |
| 10 | Sort Array By Parity | Easy | Solve |
| 11 | Height Checker | Easy | Solve |
| 12 | Relative Sort Array | Easy | Solve |
| 13 | Make Two Arrays Equal by Reversing Subarrays | Easy | Solve |
| 14 | Minimum Absolute Difference | Easy | Solve |
| 15 | Sort Integers by The Number of 1 Bits | Easy | Solve |
| 16 | Sort Colors | Medium | Solve |
| 17 | Merge Intervals | Medium | Solve |
| 18 | Kth Largest Element in an Array | Medium | Solve |
| 19 | Top K Frequent Elements | Medium | Solve |
| 20 | Sort Characters By Frequency | Medium | Solve |
| 21 | K Closest Points to Origin | Medium | Solve |
| 22 | Largest Number | Medium | Solve |
| 23 | Wiggle Sort II | Medium | Solve |
| 24 | Pancake Sorting | Medium | Solve |
| 25 | Custom Sort String | Medium | Solve |
| 26 | Reverse Pairs | Hard | Solve |
| 27 | Count of Smaller Numbers After Self | Hard | Solve |
| 28 | Maximum Gap | Hard | Solve |
| 29 | Data Stream as Disjoint Intervals | Hard | Solve |
| 30 | Minimum Number of Operations to Sort a Binary Tree by Level | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Two Sum | Easy | Solve |
| 2 | Valid Anagram | Easy | Solve |
| 3 | Contains Duplicate | Easy | Solve |
| 4 | Replace Elements with Greatest Element on Right Side | Easy | Solve |
| 5 | Is Subsequence | Easy | Solve |
| 6 | Length of Last Word | Easy | Solve |
| 7 | Longest Common Prefix | Easy | Solve |
| 8 | Pascal's Triangle | Easy | Solve |
| 9 | Remove Element | Easy | Solve |
| 10 | Majority Element | Easy | Solve |
| 11 | Find Pivot Index | Easy | Solve |
| 12 | Find All Numbers Disappeared in an Array | Easy | Solve |
| 13 | Squares of a Sorted Array | Easy | Solve |
| 14 | Move Zeroes | Easy | Solve |
| 15 | Intersection of Two Arrays | Easy | Solve |
| 16 | Group Anagrams | Medium | Solve |
| 17 | Top K Frequent Elements | Medium | Solve |
| 18 | Product of Array Except Self | Medium | Solve |
| 19 | Valid Sudoku | Medium | Solve |
| 20 | Longest Consecutive Sequence | Medium | Solve |
| 21 | Sort Colors | Medium | Solve |
| 22 | Subarray Sum Equals K | Medium | Solve |
| 23 | Next Permutation | Medium | Solve |
| 24 | Rotate Image | Medium | Solve |
| 25 | Set Matrix Zeroes | Medium | Solve |
| 26 | First Missing Positive | Hard | Solve |
| 27 | Trapping Rain Water | Hard | Solve |
| 28 | Sudoku Solver | Hard | Solve |
| 29 | N-Queens | Hard | Solve |
| 30 | Largest Rectangle in Histogram | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Valid Palindrome | Easy | Solve |
| 2 | Reverse String | Easy | Solve |
| 3 | First Unique Character in a String | Easy | Solve |
| 4 | Isomorphic Strings | Easy | Solve |
| 5 | Word Pattern | Easy | Solve |
| 6 | Add Strings | Easy | Solve |
| 7 | Reverse Vowels of a String | Easy | Solve |
| 8 | Valid Palindrome II | Easy | Solve |
| 9 | Check If Two String Arrays are Equivalent | Easy | Solve |
| 10 | Goal Parser Interpretation | Easy | Solve |
| 11 | Defanging an IP Address | Easy | Solve |
| 12 | Shuffle String | Easy | Solve |
| 13 | Split a String in Balanced Strings | Easy | Solve |
| 14 | Longest Palindrome | Easy | Solve |
| 15 | Roman to Integer | Easy | Solve |
| 16 | Longest Substring Without Repeating Characters | Medium | Solve |
| 17 | Longest Palindromic Substring | Medium | Solve |
| 18 | String to Integer (atoi) | Medium | Solve |
| 19 | Zigzag Conversion | Medium | Solve |
| 20 | Find All Anagrams in a String | Medium | Solve |
| 21 | Permutation in String | Medium | Solve |
| 22 | Minimum Number of Steps to Make Two Strings Anagram | Medium | Solve |
| 23 | Decode String | Medium | Solve |
| 24 | Palindromic Substrings | Medium | Solve |
| 25 | Multiply Strings | Medium | Solve |
| 26 | Minimum Window Substring | Hard | Solve |
| 27 | Wildcard Matching | Hard | Solve |
| 28 | Regular Expression Matching | Hard | Solve |
| 29 | Longest Valid Parentheses | Hard | Solve |
| 30 | Edit Distance | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Best Time to Buy and Sell Stock | Easy | Solve |
| 2 | Valid Palindrome | Easy | Solve |
| 3 | Merge Sorted Array | Easy | Solve |
| 4 | Reverse String | Easy | Solve |
| 5 | Move Zeroes | Easy | Solve |
| 6 | Minimum Difference Between Highest and Lowest of K Scores | Easy | Solve |
| 7 | Substrings of Size Three with Distinct Characters | Easy | Solve |
| 8 | Maximum Average Subarray I | Easy | Solve |
| 9 | Find the K-Beauty of a Number | Easy | Solve |
| 10 | Minimum Recolors to Get K Consecutive Black Blocks | Easy | Solve |
| 11 | Longest Nice Substring | Easy | Solve |
| 12 | Two Sum II - Input Array Is Sorted | Easy | Solve |
| 13 | Remove Duplicates from Sorted Array | Easy | Solve |
| 14 | Reverse Words in a String III | Easy | Solve |
| 15 | Intersection of Two Arrays II | Easy | Solve |
| 16 | Container With Most Water | Medium | Solve |
| 17 | 3Sum | Medium | Solve |
| 18 | Longest Substring Without Repeating Characters | Medium | Solve |
| 19 | Longest Repeating Character Replacement | Medium | Solve |
| 20 | Max Consecutive Ones III | Medium | Solve |
| 21 | Fruit Into Baskets | Medium | Solve |
| 22 | Permutation in String | Medium | Solve |
| 23 | Find All Anagrams in a String | Medium | Solve |
| 24 | Subarray Product Less Than K | Medium | Solve |
| 25 | Minimum Size Subarray Sum | Medium | Solve |
| 26 | Sliding Window Maximum | Hard | Solve |
| 27 | Minimum Window Substring | Hard | Solve |
| 28 | Subarrays with K Different Integers | Hard | Solve |
| 29 | Minimum Window Subsequence | Hard | Solve |
| 30 | Substring with Concatenation of All Words | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Binary Search | Easy | Solve |
| 2 | First Bad Version | Easy | Solve |
| 3 | Search Insert Position | Easy | Solve |
| 4 | Guess Number Higher or Lower | Easy | Solve |
| 5 | Valid Perfect Square | Easy | Solve |
| 6 | Arranging Coins | Easy | Solve |
| 7 | Find Smallest Letter Greater Than Target | Easy | Solve |
| 8 | Peak Index in a Mountain Array | Easy | Solve |
| 9 | Kth Missing Positive Number | Easy | Solve |
| 10 | Count Negative Numbers in a Sorted Matrix | Easy | Solve |
| 11 | Special Array With X Elements Greater Than or Equal X | Easy | Solve |
| 12 | Check If N and Its Double Exist | Easy | Solve |
| 13 | The K Weakest Rows in a Matrix | Easy | Solve |
| 14 | Find Target Indices After Sorting Array | Easy | Solve |
| 15 | Find Distance Value Between Two Arrays | Easy | Solve |
| 16 | Search a 2D Matrix | Medium | Solve |
| 17 | Search in Rotated Sorted Array | Medium | Solve |
| 18 | Find Minimum in Rotated Sorted Array | Medium | Solve |
| 19 | Find First and Last Position of Element in Sorted Array | Medium | Solve |
| 20 | Koko Eating Bananas | Medium | Solve |
| 21 | Find Peak Element | Medium | Solve |
| 22 | Time Based Key-Value Store | Medium | Solve |
| 23 | Capacity To Ship Packages Within D Days | Medium | Solve |
| 24 | Minimum Number of Days to Make m Bouquets | Medium | Solve |
| 25 | Single Element in a Sorted Array | Medium | Solve |
| 26 | Median of Two Sorted Arrays | Hard | Solve |
| 27 | Find in Mountain Array | Hard | Solve |
| 28 | Split Array Largest Sum | Hard | Solve |
| 29 | Find Minimum in Rotated Sorted Array II | Hard | Solve |
| 30 | Kth Smallest Element in a Sorted Matrix | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Reverse Linked List | Easy | Solve |
| 2 | Merge Two Sorted Lists | Easy | Solve |
| 3 | Linked List Cycle | Easy | Solve |
| 4 | Middle of the Linked List | Easy | Solve |
| 5 | Palindrome Linked List | Easy | Solve |
| 6 | Remove Linked List Elements | Easy | Solve |
| 7 | Intersection of Two Linked Lists | Easy | Solve |
| 8 | Delete Node in a Linked List | Easy | Solve |
| 9 | Remove Duplicates from Sorted List | Easy | Solve |
| 10 | Convert Binary Number in a Linked List to Integer | Easy | Solve |
| 11 | Design HashSet | Easy | Solve |
| 12 | Design HashMap | Easy | Solve |
| 13 | Print the Elements of a Linked List | Easy | Solve |
| 14 | Insert a Node at the Tail of a Linked List | Easy | Solve |
| 15 | Insert a Node at the Head of a Linked List | Easy | Solve |
| 16 | Add Two Numbers | Medium | Solve |
| 17 | Copy List with Random Pointer | Medium | Solve |
| 18 | LRU Cache | Medium | Solve |
| 19 | Remove Nth Node From End of List | Medium | Solve |
| 20 | Reorder List | Medium | Solve |
| 21 | Find the Duplicate Number | Medium | Solve |
| 22 | Swap Nodes in Pairs | Medium | Solve |
| 23 | Rotate List | Medium | Solve |
| 24 | Partition List | Medium | Solve |
| 25 | Sort List | Medium | Solve |
| 26 | Merge k Sorted Lists | Hard | Solve |
| 27 | Reverse Nodes in k-Group | Hard | Solve |
| 28 | LFU Cache | Hard | Solve |
| 29 | All O`one Data Structure | Hard | Solve |
| 30 | Design Skiplist | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Valid Parentheses | Easy | Solve |
| 2 | Implement Queue using Stacks | Easy | Solve |
| 3 | Implement Stack using Queues | Easy | Solve |
| 4 | Min Stack | Medium | Solve |
| 5 | Next Greater Element I | Easy | Solve |
| 6 | Baseball Game | Easy | Solve |
| 7 | Backspace String Compare | Easy | Solve |
| 8 | Remove All Adjacent Duplicates In String | Easy | Solve |
| 9 | Make The String Great | Easy | Solve |
| 10 | Crawler Log Folder | Easy | Solve |
| 11 | Number of Students Unable to Eat Lunch | Easy | Solve |
| 12 | Time Needed to Buy Tickets | Easy | Solve |
| 13 | First Unique Character in a String | Easy | Solve |
| 14 | Number of Recent Calls | Easy | Solve |
| 15 | Design Parking System | Easy | Solve |
| 16 | Evaluate Reverse Polish Notation | Medium | Solve |
| 17 | Daily Temperatures | Medium | Solve |
| 18 | Decode String | Medium | Solve |
| 19 | Asteroid Collision | Medium | Solve |
| 20 | Design Circular Queue | Medium | Solve |
| 21 | Design Circular Deque | Medium | Solve |
| 22 | Minimum Remove to Make Valid Parentheses | Medium | Solve |
| 23 | 132 Pattern | Medium | Solve |
| 24 | Online Stock Span | Medium | Solve |
| 25 | Simplify Path | Medium | Solve |
| 26 | Largest Rectangle in Histogram | Hard | Solve |
| 27 | Maximal Rectangle | Hard | Solve |
| 28 | Sliding Window Maximum | Hard | Solve |
| 29 | Trapping Rain Water | Hard | Solve |
| 30 | Design a Text Editor | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Last Stone Weight | Easy | Solve |
| 2 | Kth Largest Element in a Stream | Easy | Solve |
| 3 | Relative Ranks | Easy | Solve |
| 4 | The K Weakest Rows in a Matrix | Easy | Solve |
| 5 | Maximum Product of Two Elements in an Array | Easy | Solve |
| 6 | Make Array Zero by Subtracting Equal Amounts | Easy | Solve |
| 7 | Take Gifts From the Richest Pile | Easy | Solve |
| 8 | Delete Greatest Value in Each Row | Easy | Solve |
| 9 | Minimum Amount of Time to Fill Cups | Easy | Solve |
| 10 | Minimum Operations to Halve Array Sum | Medium | Solve |
| 11 | Sorting the Sentence | Easy | Solve |
| 12 | Find Subsequence of Length K With the Largest Sum | Easy | Solve |
| 13 | Maximum Units on a Truck | Easy | Solve |
| 14 | Keep Multiplying Found Values by Two | Easy | Solve |
| 15 | Kth Distinct String in an Array | Easy | Solve |
| 16 | Top K Frequent Elements | Medium | Solve |
| 17 | Kth Largest Element in an Array | Medium | Solve |
| 18 | Find K Pairs with Smallest Sums | Medium | Solve |
| 19 | Task Scheduler | Medium | Solve |
| 20 | Reorganize String | Medium | Solve |
| 21 | K Closest Points to Origin | Medium | Solve |
| 22 | Sort Characters By Frequency | Medium | Solve |
| 23 | Top K Frequent Words | Medium | Solve |
| 24 | Ugly Number II | Medium | Solve |
| 25 | Find the Kth Largest Integer in the Array | Medium | Solve |
| 26 | Merge k Sorted Lists | Hard | Solve |
| 27 | Find Median from Data Stream | Hard | Solve |
| 28 | Sliding Window Maximum | Hard | Solve |
| 29 | IPO | Hard | Solve |
| 30 | Trapping Rain Water II | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Binary Watch | Easy | Solve |
| 2 | Sum of All Subset XOR Totals | Easy | Solve |
| 3 | Pascal's Triangle | Easy | Solve |
| 4 | Pascal's Triangle II | Easy | Solve |
| 5 | Find All Paths | Easy | Solve |
| 6 | Minimum Distance Between BST Nodes | Easy | Solve |
| 7 | Increasing Order Search Tree | Easy | Solve |
| 8 | Leaf-Similar Trees | Easy | Solve |
| 9 | Univalued Binary Tree | Easy | Solve |
| 10 | Cousins in Binary Tree | Easy | Solve |
| 11 | Find Mode in Binary Search Tree | Easy | Solve |
| 12 | Construct String from Binary Tree | Easy | Solve |
| 13 | Average of Levels in Binary Tree | Easy | Solve |
| 14 | Binary Tree Tilt | Easy | Solve |
| 15 | Diameter of Binary Tree | Easy | Solve |
| 16 | Subsets | Medium | Solve |
| 17 | Permutations | Medium | Solve |
| 18 | Combination Sum | Medium | Solve |
| 19 | Word Search | Medium | Solve |
| 20 | Combinations | Medium | Solve |
| 21 | Subsets II | Medium | Solve |
| 22 | Permutations II | Medium | Solve |
| 23 | Combination Sum II | Medium | Solve |
| 24 | Combination Sum III | Medium | Solve |
| 25 | Letter Combinations of a Phone Number | Medium | Solve |
| 26 | N-Queens | Hard | Solve |
| 27 | Sudoku Solver | Hard | Solve |
| 28 | Word Search II | Hard | Solve |
| 29 | N-Queens II | Hard | Solve |
| 30 | Remove Invalid Parentheses | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Assign Cookies | Easy | Solve |
| 2 | Lemonade Change | Easy | Solve |
| 3 | Array Partition | Easy | Solve |
| 4 | Maximum 69 Number | Easy | Solve |
| 5 | Minimum Cost to Move Chips to The Same Position | Easy | Solve |
| 6 | Split a String in Balanced Strings | Easy | Solve |
| 7 | Minimum Time to Type Word Using Special Typewriter | Easy | Solve |
| 8 | Minimum Moves to Convert String | Easy | Solve |
| 9 | Maximum Number of Words You Can Type | Easy | Solve |
| 10 | Minimum Operations to Make the Array Increasing | Easy | Solve |
| 11 | Calculate Money in Leetcode Bank | Easy | Solve |
| 12 | Maximum Units on a Truck | Easy | Solve |
| 13 | Water Bottles | Easy | Solve |
| 14 | Apple Redistribution into Boxes | Easy | Solve |
| 15 | Largest Odd Number in String | Easy | Solve |
| 16 | Jump Game | Medium | Solve |
| 17 | Gas Station | Medium | Solve |
| 18 | Task Scheduler | Medium | Solve |
| 19 | Partition Labels | Medium | Solve |
| 20 | Jump Game II | Medium | Solve |
| 21 | Non-overlapping Intervals | Medium | Solve |
| 22 | Minimum Number of Arrows to Burst Balloons | Medium | Solve |
| 23 | Reorganize String | Medium | Solve |
| 24 | Advantage Shuffle | Medium | Solve |
| 25 | Maximum Length of Pair Chain | Medium | Solve |
| 26 | Candy | Hard | Solve |
| 27 | IPO | Hard | Solve |
| 28 | Course Schedule III | Hard | Solve |
| 29 | Minimum Number of Refueling Stops | Hard | Solve |
| 30 | Maximum Profit in Job Scheduling | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Maximum Depth of Binary Tree | Easy | Solve |
| 2 | Invert Binary Tree | Easy | Solve |
| 3 | Diameter of Binary Tree | Easy | Solve |
| 4 | Balanced Binary Tree | Easy | Solve |
| 5 | Same Tree | Easy | Solve |
| 6 | Subtree of Another Tree | Easy | Solve |
| 7 | Lowest Common Ancestor of a Binary Search Tree | Easy | Solve |
| 8 | Path Sum | Easy | Solve |
| 9 | Minimum Depth of Binary Tree | Easy | Solve |
| 10 | Symmetric Tree | Easy | Solve |
| 11 | Binary Tree Paths | Easy | Solve |
| 12 | Search in a Binary Search Tree | Easy | Solve |
| 13 | Merge Two Binary Trees | Easy | Solve |
| 14 | Two Sum IV - Input is a BST | Easy | Solve |
| 15 | Convert Sorted Array to Binary Search Tree | Easy | Solve |
| 16 | Lowest Common Ancestor of a Binary Tree | Medium | Solve |
| 17 | Binary Tree Level Order Traversal | Medium | Solve |
| 18 | Binary Tree Right Side View | Medium | Solve |
| 19 | Count Good Nodes in Binary Tree | Medium | Solve |
| 20 | Validate Binary Search Tree | Medium | Solve |
| 21 | Kth Smallest Element in a BST | Medium | Solve |
| 22 | Construct Binary Tree from Preorder and Inorder Traversal | Medium | Solve |
| 23 | Binary Tree Zigzag Level Order Traversal | Medium | Solve |
| 24 | Flatten Binary Tree to Linked List | Medium | Solve |
| 25 | Populating Next Right Pointers in Each Node | Medium | Solve |
| 26 | Binary Tree Maximum Path Sum | Hard | Solve |
| 27 | Serialize and Deserialize Binary Tree | Hard | Solve |
| 28 | Word Ladder | Hard | Solve |
| 29 | Recover Binary Search Tree | Hard | Solve |
| 30 | Vertical Order Traversal of a Binary Tree | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Island Perimeter | Easy | Solve |
| 2 | Find the Town Judge | Easy | Solve |
| 3 | Flood Fill | Easy | Solve |
| 4 | Find if Path Exists in Graph | Easy | Solve |
| 5 | Maximum Depth of N-ary Tree | Easy | Solve |
| 6 | Employee Importance | Easy | Solve |
| 7 | Cousins in Binary Tree | Easy | Solve |
| 8 | Minimum Number of Vertices to Reach All Nodes | Easy | Solve |
| 9 | Water Bottles | Easy | Solve |
| 10 | Number of Provinces | Easy | Solve |
| 11 | Graph Valid Tree (Premium) | Easy | Solve |
| 12 | Number of Connected Components in an Undirected Graph | Easy | Solve |
| 13 | Path With Minimum Effort | Easy | Solve |
| 14 | Matrix Diagonal Sum | Easy | Solve |
| 15 | Find Center of Star Graph | Easy | Solve |
| 16 | Number of Islands | Medium | Solve |
| 17 | Max Area of Island | Medium | Solve |
| 18 | Clone Graph | Medium | Solve |
| 19 | Walls and Gates | Medium | Solve |
| 20 | Rotting Oranges | Medium | Solve |
| 21 | Pacific Atlantic Water Flow | Medium | Solve |
| 22 | Surrounded Regions | Medium | Solve |
| 23 | Course Schedule | Medium | Solve |
| 24 | Course Schedule II | Medium | Solve |
| 25 | Network Delay Time | Medium | Solve |
| 26 | Word Ladder | Hard | Solve |
| 27 | Minimum Degree of a Connected Trio in a Graph | Hard | Solve |
| 28 | Alien Dictionary | Hard | Solve |
| 29 | Cheapest Flights Within K Stops | Hard | Solve |
| 30 | Longest Increasing Path in a Matrix | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Climbing Stairs | Easy | Solve |
| 2 | Min Cost Climbing Stairs | Easy | Solve |
| 3 | Fibonacci Number | Easy | Solve |
| 4 | N-th Tribonacci Number | Easy | Solve |
| 5 | Maximum Subarray | Easy | Solve |
| 6 | Best Time to Buy and Sell Stock | Easy | Solve |
| 7 | Is Subsequence | Easy | Solve |
| 8 | Counting Bits | Easy | Solve |
| 9 | Pascal's Triangle | Easy | Solve |
| 10 | Pascal's Triangle II | Easy | Solve |
| 11 | Divisor Game | Easy | Solve |
| 12 | Get Maximum in Generated Array | Easy | Solve |
| 13 | Maximum Score After Splitting a String | Easy | Solve |
| 14 | Decode Ways | Easy | Solve |
| 15 | Coin Change | Easy | Solve |
| 16 | Coin Change II | Medium | Solve |
| 17 | Longest Increasing Subsequence | Medium | Solve |
| 18 | Longest Common Subsequence | Medium | Solve |
| 19 | Word Break | Medium | Solve |
| 20 | Combination Sum IV | Medium | Solve |
| 21 | House Robber | Medium | Solve |
| 22 | House Robber II | Medium | Solve |
| 23 | Palindromic Substrings | Medium | Solve |
| 24 | Unique Paths | Medium | Solve |
| 25 | Maximum Product Subarray | Medium | Solve |
| 26 | Burst Balloons | Hard | Solve |
| 27 | Regular Expression Matching | Hard | Solve |
| 28 | Longest Valid Parentheses | Hard | Solve |
| 29 | Edit Distance | Hard | Solve |
| 30 | Maximum Profit in Job Scheduling | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Longest Common Prefix | Easy | Solve |
| 2 | Count Prefixes of a Given String | Easy | Solve |
| 3 | Check If a Word Occurs As a Prefix of Any Word in a Sentence | Easy | Solve |
| 4 | Find Resultant Array After Removing Anagrams | Easy | Solve |
| 5 | Maximum Number of Words Found in Sentences | Easy | Solve |
| 6 | Sorting the Sentence | Easy | Solve |
| 7 | Truncate Sentence | Easy | Solve |
| 8 | Check if All Characters Have Equal Number of Occurrences | Easy | Solve |
| 9 | Destination City | Easy | Solve |
| 10 | Jewels and Stones | Easy | Solve |
| 11 | Unique Morse Code Words | Easy | Solve |
| 12 | Uncommon Words from Two Sentences | Easy | Solve |
| 13 | Find Words That Can Be Formed by Characters | Easy | Solve |
| 14 | Path Crossing | Easy | Solve |
| 15 | Check If Two String Arrays are Equivalent | Easy | Solve |
| 16 | Implement Trie (Prefix Tree) | Medium | Solve |
| 17 | Design Add and Search Words Data Structure | Medium | Solve |
| 18 | Replace Words | Medium | Solve |
| 19 | Maximum XOR of Two Numbers in an Array | Medium | Solve |
| 20 | Search Suggestions System | Medium | Solve |
| 21 | Map Sum Pairs | Medium | Solve |
| 22 | Camelcase Matching | Medium | Solve |
| 23 | Remove Sub-Folders from the Filesystem | Medium | Solve |
| 24 | Implement Magic Dictionary | Medium | Solve |
| 25 | Longest Word in Dictionary | Medium | Solve |
| 26 | Word Search II | Hard | Solve |
| 27 | Palindrome Pairs | Hard | Solve |
| 28 | Stream of Characters | Hard | Solve |
| 29 | Design Search Autocomplete System | Hard | Solve |
| 30 | Prefix and Suffix Search | Hard | Solve |
| No. | Problem Name | Difficulty | Action |
|---|---|---|---|
| 1 | Design Parking System | Easy | Solve |
| 2 | Design HashSet | Easy | Solve |
| 3 | Design HashMap | Easy | Solve |
| 4 | Range Sum Query - Immutable | Easy | Solve |
| 5 | Kth Largest Element in a Stream | Easy | Solve |
| 6 | Moving Average from Data Stream | Easy | Solve |
| 7 | Guess Number Higher or Lower | Easy | Solve |
| 8 | First Bad Version | Easy | Solve |
| 9 | Is Bad Version | Easy | Solve |
| 10 | Logger Rate Limiter | Easy | Solve |
| 11 | Roman to Integer | Easy | Solve |
| 12 | Implement Queue using Stacks | Easy | Solve |
| 13 | Implement Stack using Queues | Easy | Solve |
| 14 | Min Stack | Medium | Solve |
| 15 | Valid Sudoku | Medium | Solve |
| 16 | LRU Cache | Medium | Solve |
| 17 | Insert Delete GetRandom O(1) | Medium | Solve |
| 18 | Design Tic-Tac-Toe | Medium | Solve |
| 19 | Design Underground System | Medium | Solve |
| 20 | Design Browser History | Medium | Solve |
| 21 | Design a Number Container System | Medium | Solve |
| 22 | Encode and Decode Strings | Medium | Solve |
| 23 | Flatten Nested List Iterator | Medium | Solve |
| 24 | Time Based Key-Value Store | Medium | Solve |
| 25 | Snapshot Array | Medium | Solve |
| 26 | LFU Cache | Hard | Solve |
| 27 | All O`one Data Structure | Hard | Solve |
| 28 | Design In-Memory File System | Hard | Solve |
| 29 | Design Search Autocomplete System | Hard | Solve |
| 30 | Find Median from Data Stream | Hard | Solve |