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Unlock the secrets of Data Structures and Algorithms with these powerful patterns! ๐ŸŒŸOnce you grasp these, solving DSA problems becomes a breeze. Here are 20 essential coding patterns you need to know:
1. โœŒ๏ธ Two Pointers
2. ๐Ÿ๏ธ Island (Matrix Traversal)
3. โฉ Fast & Slow Pointer
4. ๐Ÿšถโ€โ™‚๏ธ Sliding Window
5. ๐Ÿ“… Merge Intervals
6. ๐Ÿ”„ Cyclic Sort
7. ๐Ÿ”™ In-place Reversal of a Linked List
8. ๐ŸŒณ Tree Breadth First Search
9. ๐ŸŒฒ Tree Depth First Search
10. โš–๏ธ Two Heaps
11. ๐ŸŒˆ Subsets
12. ๐Ÿ” Modified Binary Search
13. ๐Ÿ† Top โ€˜Kโ€™ Elements
14. โŒโญ• Bitwise XOR
15. ๐Ÿ”„ Backtracking
16. ๐ŸŽ’ 0/1 Knapsack (Dynamic Programming)
17. ๐Ÿ”— Topological Sort (Graph)
18. ๐Ÿงฉ K-way Merge
19. ๐Ÿ“ Monotonic Stack
20. ๐Ÿคนโ€โ™‚๏ธ Multi-threaded
Common DSA Patterns Syllabus: [Level Easy]

1. Arrays & Strings  
 - Two Sum   
 - Valid Parentheses   
 - Group Anagrams
2. Linked Lists   
- Reverse Linked List   
- Merge Two Sorted Lists   
- Linked List Cycle
3. Trees   
- Maximum Depth of Binary Tree   
- Validate Binary Search Tree   
- Lowest Common Ancestor of BST
4. Dynamic Programming   
- Climbing Stairs   
- Coin Change   
- Longest Increasing Subsequence

5. Graphs   
- Clone Graph   
- Course Schedule   
- Number of Islands

6. Recursion & Backtracking   
- Subsets   
- Permutations   
- N-Queens

7. Sorting & Searching   
- Merge Intervals   
- Search in Rotated Sorted Array   
- Kth Largest Element in an Array

8. Design   
- LRU Cache   
- Implement Trie (Prefix Tree)   
- Design Twitter

Solve these questions consistently, understand the patterns, and optimize your solutions. Remember, quality over quantity!
[Level Medium]

1. Arrays & Strings
- 3Sum
- Longest Substring Without Repeating Characters
- Minimum Window Substring\

2. Linked Lists
- Add Two Numbers
- Reorder List
- Copy List with Random Pointer

3. Trees
- Binary Tree Level Order Traversal
- Kth Smallest Element in a BST
- Serialize and Deserialize Binary Tree

4. Dynamic Programming
- Unique Paths
- Decode Ways
- Maximum Product Subarray

5. Graphs
- Surrounded Regions
- Pacific Atlantic Water Flow
- Minimum Height Trees

6. Recursion & Backtracking
- Combination Sum
- Word Search
- Generate Parentheses

7. Sorting & Searching
- Top K Frequent Elements
- Find Peak Element
- Search a 2D Matrix II

8. Design
- Insert Delete GetRandom O(1)
- Design Underground System
- Design Tic-Tac-Toe

9. Greedy
- Jump Game
- Gas Station
- Partition Labels

10. Bit Manipulation
- Single Number II
- Bitwise AND of Numbers Range
- Counting Bits

11. Two Pointers
- 3Sum Closest
- Minimum Size Subarray Sum
- Palindromic Substrings

12. Heap
- Merge k Sorted Lists
- Top K Frequent Words
- Find Median from Data Stream
[Level Hard]
1. Arrays & Strings
- Minimum Window Substring
- Trapping Rain Water
- Largest Rectangle in Histogram

2. Linked Lists
- Merge k Sorted Lists
- Reverse Nodes in k-Group
- LFU Cache

3. Trees
- Binary Tree Maximum Path Sum
- Serialize and Deserialize Binary Tree
- Vertical Order Traversal of a Binary Tree

4. Dynamic Programming
- Edit Distance
- Burst Balloons
- Shortest Common Supersequence

5. Graphs
- Alien Dictionary
- Minimum Cost to Make at Least One Valid Path in a Grid
- Swim in Rising Water

6. Recursion & Backtracking
- N-Queens II
- Sudoku Solver
- Word Search II

7. Sorting & Searching
- Count of Smaller Numbers After Self
- Median of Two Sorted Arrays
- Split Array Largest Sum

8. Design
- Design Search Autocomplete System
- Design In-Memory File System
- Design Excel Sum Formula

9. Greedy
- Minimum Number of Arrows to Burst Balloons
- Candy
- Patching Array

10. Bit Manipulation
- Maximum Product of Word Lengths
- Smallest Sufficient Team
- Minimum Cost to Connect Two Groups of Points

11. Two Pointers
- Minimum Window Subsequence
- Minimum Operations to Make a Subsequence
- Minimum Adjacent Swaps to Reach the Kth Smallest Number

12. Heap
- Minimum Number of Refueling Stops
- Sliding Window Median
- Minimum Number of K Consecutive Bit Flips
1. Two Sum (LeetCode #1)

- Hash table for efficient lookup

2. Best Time to Buy and Sell Stock (LeetCode #121)

- Track minimum price and maximum profit

3. Product of Array Except Self (LeetCode #238)

- Left and right product arrays

4. Maximum Subarray (LeetCode #53)

- Kadaneโ€™s algorithm

5. Find Minimum in Rotated Sorted Array (LeetCode #153)

- Modified binary search

6. Search in Rotated Sorted Array (LeetCode #33)

- Two-pass binary search

7. Subarray Sum Equals K (LeetCode #560)

- Cumulative sum with hash map

8. Merge Sorted Array (LeetCode #88)

- Start from end, compare and place

9. Find All Numbers Disappeared in an Array (LeetCode #448)

- In-place array manipulation