1. 1. Introduction
2. 2. Arrays and Hashing
3. 1. 2.1. Contains Duplicate
   2. 2.2. Valid Anagram
   3. 2.3. Two Sum
   4. 2.4. Group Anagrams
   5. 2.5. Top K Frequent Elements
   6. 2.6. Product of Array Except Self
   7. 2.7. Valid Sudoku
   8. 2.8. Encode and Decode Strings
   9. 2.9. Longest Consecutive Sequence
4. 3. Two Pointers
5. 1. 3.1. Valid Palindrome
   2. 3.2. Two Sum II - Input Array Is Sorted
   3. 3.3. 3Sum
   4. 3.4. Container With Most Water
   5. 3.5. Trapping Rain Water
6. 4. Sliding Window
7. 1. 4.1. Best Time to Buy and Sell Stock
   2. 4.2. Longest Substring Without Repeating Characters
   3. 4.3. Longest Repeating Character Replacement
   4. 4.4. Permutation in String
   5. 4.5. Minimum Window Substring
   6. 4.6. Sliding Window Maximum
8. 5. Stack
9. 1. 5.1. Valid Parentheses
   2. 5.2. Min Stack
   3. 5.3. Evaluate Reverse Polish Notation
   4. 5.4. Generate Parentheses
   5. 5.5. Daily Temperatures
   6. 5.6. Car Fleet
   7. 5.7. Largest Rectangle In Histogram
10. 6. Binary Search
11. 1. 6.1. Binary Search
    2. 6.2. Search a 2D Matrix
    3. 6.3. Koko Eating Bananas
    4. 6.4. Find Minimum In Rotated Sorted Array
    5. 6.5. Search In Rotated Sorted Array
    6. 6.6. Time Based Key Value Store
    7. 6.7. Median of Two Sorted Arrays
12. 7. Linked List
13. 1. 7.1. Reverse Linked List
    2. 7.2. Merge Two Sorted Lists
    3. 7.3. Reorder List
    4. 7.4. Remove Nth Node From End of List
    5. 7.5. Copy List With Random Pointer
    6. 7.6. Add Two Numbers
    7. 7.7. Linked List Cycle
    8. 7.8. Find The Duplicate Number
    9. 7.9. LRU Cache
    10. 7.10. Merge K Sorted Lists
    11. 7.11. Reverse Nodes In K Group
14. 8. Trees
15. 1. 8.1. Invert Binary Tree
    2. 8.2. Maximum Depth of Binary Tree
    3. 8.3. Diameter of Binary Tree
    4. 8.4. Balanced Binary Tree
    5. 8.5. Same Tree
    6. 8.6. Subtree of Another Tree
    7. 8.7. Lowest Common Ancestor of a Binary Search Tree
    8. 8.8. Binary Tree Level Order Traversal
    9. 8.9. Binary Tree Right Side View
    10. 8.10. Count Good Nodes In Binary Tree
    11. 8.11. Validate Binary Search Tree
    12. 8.12. Kth Smallest Element In a BST
    13. 8.13. Construct Binary Tree from Preorder and Inorder Traversal
    14. 8.14. Binary Tree Maximum Path Sum
    15. 8.15. Serialize and Deserialize Binary Tree
16. 9. Tries
17. 1. 9.1. Implement Trie Prefix Tree
    2. 9.2. Design Add and Search Words Data Structure
    3. 9.3. Word Search II
18. 10. Heap Priority Queues
19. 1. 10.1. Kth Largest Element in a Stream
    2. 10.2. Last Stone Weight
    3. 10.3. K Closest Points to Origin
    4. 10.4. Kth Largest Element in an Array
    5. 10.5. Task Scheduler
    6. 10.6. Design Twitter
    7. 10.7. Find Median from Data Stream
20. 11. Backtracking
21. 1. 11.1. Subsets
    2. 11.2. Combination Sum
    3. 11.3. Permutations
    4. 11.4. Subsets II
    5. 11.5. Combination Sum II
    6. 11.6. Word Search
    7. 11.7. Palindrome Partitioning
    8. 11.8. Letter Combinations of a Phone Number
    9. 11.9. N Queens
22. 12. Graphs
23. 1. 12.1. Number of Islands
    2. 12.2. Clone Graph
    3. 12.3. Max Area of Island
    4. 12.4. Pacific Atlantic Water Flow
    5. 12.5. Surrounded Regions
    6. 12.6. Rotting Oranges
    7. 12.7. Walls and Gates
    8. 12.8. Course Schedule
    9. 12.9. Course Schedule II
    10. 12.10. Redundant Connection
    11. 12.11. Number of Connected Components in an Undirected Graph
    12. 12.12. Graph Valid Tree
    13. 12.13. Word Ladder
24. 13. Advanced Graphs
25. 1. 13.1. Reconstruct Itinerary
    2. 13.2. Min Cost to Connect All Points
    3. 13.3. Network Delay Time
    4. 13.4. Swim in Rising Water
    5. 13.5. Alien Dictionary
    6. 13.6. Cheapest Flights Within K Stops
26. 14. 1-D Dynamic Programming
27. 1. 14.1. Climbing Stairs
    2. 14.2. Min Cost Climbing Stairs
    3. 14.3. House Robber
    4. 14.4. House Robber II
    5. 14.5. Longest Palindromic Substring
    6. 14.6. Palindromic Substrings
    7. 14.7. Decode Ways
    8. 14.8. Coin Change
    9. 14.9. Maximum Product Subarray
    10. 14.10. Word Break
    11. 14.11. Longest Increasing Subsequence
    12. 14.12. Partition Equal Subset Sum
28. 15. 2-D Dynamic Programming
29. 1. 15.1. Unique Paths
    2. 15.2. Longest Common Subsequence
    3. 15.3. Best Time to Buy And Sell Stock With Cooldown
    4. 15.4. Coin Change II
    5. 15.5. Target Sum
    6. 15.6. Interleaving String
    7. 15.7. Longest Increasing Path In a Matrix
    8. 15.8. Distinct Subsequences
    9. 15.9. Edit Distance
    10. 15.10. Burst Balloons
    11. 15.11. Regular Expression Matching
30. 16. Greedy
31. 1. 16.1. Maximum Subarray
    2. 16.2. Jump Game
    3. 16.3. Jump Game II
    4. 16.4. Gas Station
    5. 16.5. Hand of Straights
    6. 16.6. Merge Triplets to Form Target Triplet
    7. 16.7. Partition Labels
    8. 16.8. Valid Parenthesis String
32. 17. Intervals
33. 1. 17.1. Insert Interval
    2. 17.2. Merge Intervals
    3. 17.3. Non Overlapping Intervals
    4. 17.4. Meeting Rooms
    5. 17.5. Meeting Rooms II
    6. 17.6. Minimum Interval to Include Each Query
34. 18. Math and Geometry
35. 1. 18.1. Rotate Image
    2. 18.2. Spiral Matrix
    3. 18.3. Set Matrix Zeroes
    4. 18.4. Happy Number
    5. 18.5. Plus One
    6. 18.6. Pow(x,n)
    7. 18.7. Multiply Strings
    8. 18.8. Detect Squares
36. 19. Bit Manipulation
37. 1. 19.1. Single Number
    2. 19.2. Number of 1 Bits
    3. 19.3. Counting Bits
    4. 19.4. Reverse Bits
    5. 19.5. Missing Number
    6. 19.6. Sum of Two Integers
    7. 19.7. Reverse Integer