@@ -9,25 +9,96 @@ Do not memorize the code! Try to solve the problem for 30 minutes. If you get st
 
 ### 1. Arrays & Hashing (The Basics)
 - [ ] Two Sum (Use a HashMap)
-- [ ] Valid Anagram (Count frequencies)
+- [ ] Best Time to Buy & Sell Stock (Track min price)
 - [ ] Contains Duplicate (Use a HashSet)
-- [ ] Group Anagrams (Sort the string to use as a HashMap key)
-- [ ] Top K Frequent Elements (Use a PriorityQueue / MinHeap)
 - [ ] Product of Array Except Self (Prefix and Postfix arrays)
-- [ ] Longest Consecutive Sequence (Use a HashSet for O(1) lookups)
-
-### 2. Two Pointers (The Squeezer)
-- [ ] Valid Palindrome (Left and Right pointers moving inwards)
+- [ ] Maximum Subarray (Kadane's Algorithm)
+- [ ] Maximum Product Subarray (Track min and max)
+- [ ] Find Minimum in Rotated Sorted Array (Binary Search)
+- [ ] Search in Rotated Sorted Array (Modified Binary Search)
 - [ ] 3Sum (Sort first, then use Two Pointers)
 - [ ] Container With Most Water (Greedy Two Pointers)
 
-### 3. Sliding Window (The Caterpillar)
-- [ ] Best Time to Buy & Sell Stock (Track the minimum price)
-- [ ] Longest Substring Without Repeating Characters (Expand window, shrink on duplicates)
-- [ ] Longest Repeating Character Replacement
-- [ ] Minimum Window Substring (Hard)
+### 2. Binary / Bit Manipulation
+- [ ] Sum of Two Integers (Use XOR and AND)
+- [ ] Number of 1 Bits (Bit masking)
+- [ ] Counting Bits (DP with bits)
+- [ ] Missing Number (XOR all numbers)
+- [ ] Reverse Bits (Shift and OR)
+
+### 3. Dynamic Programming (1D & 2D)
+- [ ] Climbing Stairs (Fibonacci sequence)
+- [ ] Coin Change (Bottom-up DP)
+- [ ] Longest Increasing Subsequence (DP array)
+- [ ] Longest Common Subsequence (2D DP Grid)
+- [ ] Word Break (DP array of booleans)
+- [ ] Combination Sum IV (DP array)
+- [ ] House Robber (Keep track of two previous maxes)
+- [ ] House Robber II (Run House Robber twice)
+- [ ] Decode Ways (Fibonacci with conditions)
+- [ ] Unique Paths (2D DP Grid)
+- [ ] Jump Game (Greedy backwards)
+
+### 4. Graphs
+- [ ] Clone Graph (DFS with a HashMap)
+- [ ] Course Schedule (Topological Sort / Cycle detection)
+- [ ] Pacific Atlantic Water Flow (DFS from borders)
+- [ ] Number of Islands (DFS or BFS to sink islands)
+- [ ] Longest Consecutive Sequence (Use a HashSet for O(1) lookups)
+- [ ] Alien Dictionary (Topological Sort - Hard)
+- [ ] Graph Valid Tree (DFS cycle detection)
+- [ ] Number of Connected Components in an Undirected Graph (Disjoint Set / Union Find)
+
+### 5. Intervals
+- [ ] Insert Interval (Iterate and merge)
+- [ ] Merge Intervals (Sort by start time, merge overlaps)
+- [ ] Non-overlapping Intervals (Sort by end time, greedy approach)
+- [ ] Meeting Rooms (Sort and check overlaps)
+- [ ] Meeting Rooms II (Min-Heap for end times)
+
+### 6. Linked List
+- [ ] Reverse a Linked List (In-place pointer reversal)
+- [ ] Detect Cycle in a Linked List (Fast & Slow Pointers)
+- [ ] Merge Two Sorted Lists (Dummy node)
+- [ ] Merge K Sorted Lists (Min-Heap or Divide & Conquer)
+- [ ] Remove Nth Node From End Of List (Two Pointers separated by N gaps)
+- [ ] Reorder List (Find middle, reverse second half, merge)
+
+### 7. Matrix
+- [ ] Set Matrix Zeroes (Use first row/col as markers)
+- [ ] Spiral Matrix (Four boundaries: top, bottom, left, right)
+- [ ] Rotate Image (Transpose then reverse rows)
+- [ ] Word Search (Backtracking DFS)
+
+### 8. Strings
+- [ ] Longest Substring Without Repeating Characters (Sliding Window)
+- [ ] Longest Repeating Character Replacement (Sliding Window + Frequency Map)
+- [ ] Minimum Window Substring (Sliding Window - Hard)
+- [ ] Valid Anagram (Count frequencies)
+- [ ] Group Anagrams (Sort string to use as HashMap key)
+- [ ] Valid Parentheses (Stack)
+- [ ] Valid Palindrome (Two Pointers)
+- [ ] Longest Palindromic Substring (Expand around center)
+- [ ] Palindromic Substrings (Expand around center)
+- [ ] Encode and Decode Strings (Length prefix + delimiter)
 
-### 4. Stack
-- [ ] Valid Parentheses (Push open brackets, pop and match close brackets)
+### 9. Trees
+- [ ] Maximum Depth of Binary Tree (DFS or BFS)
+- [ ] Same Tree (Recursive DFS)
+- [ ] Invert/Flip Binary Tree (Swap left and right recursively)
+- [ ] Binary Tree Maximum Path Sum (DFS returning max straight path)
+- [ ] Binary Tree Level Order Traversal (BFS with a Queue)
+- [ ] Serialize and Deserialize Binary Tree (Preorder traversal with null markers)
+- [ ] Subtree of Another Tree (Recursive matching)
+- [ ] Construct Binary Tree from Preorder and Inorder Traversal (Recursive splitting)
+- [ ] Validate Binary Search Tree (DFS with min/max boundaries)
+- [ ] Kth Smallest Element in a BST (Inorder traversal)
+- [ ] Lowest Common Ancestor of BST (Follow the values)
+- [ ] Implement Trie (Prefix Tree) (Nodes with 26 children)
+- [ ] Add and Search Word (Trie with Backtracking for '.')
+- [ ] Word Search II (Trie + Backtracking DFS)
 
-*(Note: We will continue adding the remaining categories like Trees, Graphs, DP, and Linked Lists as we implement the code for them in this repository!)*
+### 10. Heaps
+- [ ] Merge K Sorted Lists (Min-Heap)
+- [ ] Top K Frequent Elements (Min-Heap of size K)
+- [ ] Find Median from Data Stream (Two Heaps)