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Decode the Coding Interview in Ruby: Real-World Examples

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✨Getting Started

Course Overview Who Should Take This Course?

Netflix

Project Description For Netflix Feature #1: Group Similar Titles Feature #2: Fetch Top Movies Feature #3: Find Median Age Feature #4: Popularity Analysis Feature #5: Fetch Most Recently Watched Titles Feature #6: Fetch Most Frequently Watched Titles Feature #7: Browse Ratings Feature #8: Verify User Session Feature #9: Movie Combinations of a Genre Feature #10: Calculate Median of Buffering Events Feature #11: Generate Movie Viewing Orders Feature #12: Maintain Continue Watching Bar What Did We Learn?DIY: Group Anagrams DIY: Merge K Sorted Lists DIY: Find Median from a Data Stream DIY: Monotonic Array DIY: LRU Cache DIY: LFU Cache DIY: Min Stack DIY: Validate Stack Sequences DIY: Letter Combinations of a Phone Number DIY: Sliding Window Median DIY: Permutations DIY: Maximum Frequency Stack

Facebook

Project Description for Facebook Feature #1: Friend Circles Feature #2: Copy Connections Feature #3: Find Story ID Feature #4: Request Limiter Feature #5: Flag Words Feature #6: Combine Similar Messages Feature #7: Divide Posts Feature #8: Overlapping Topics Feature #9: Recreating the Decision Tree What Did We Learn?DIY: Number of Islands DIY: Number of Provinces DIY: Number of Connected Components in an Undirected Graph DIY: Clone Directed Graph DIY: Search in Rotated Sorted Array DIY: Logger Rate Limiter DIY: Expressive words DIY: Group Shifted Strings DIY: Divide Chocolate DIY: Minimum Window Substring DIY: Construct a Binary Tree from Preorder and Inorder Traversal

Search Engine

Project Description for Search Engine Feature #1: Store and Fetch Words Feature #2: Design Search Autocomplete System Feature #3: Add White Spaces to Create Words Feature #4: Suggest Possible Queries After Adding White Spaces Feature #5: Calculate the Search Ranking Factor Feature #6: Reorganizing Search Results Feature #7: Find Searching Time Feature #8: Distributed Process Coordinator Feature #9: Finding Minimum Servers What Did We Learn?DIY: Implement Trie DIY: Suggest Relevant Sentences DIY: Word Break DIY: Word Break II DIY: Product of Array Elements Except Itself DIY: Reorganizing a String DIY: Exclusive Time of Functions DIY: Snapshot Array DIY: Coin Change DIY: Coin Change 2 DIY: Combination Sum

Google Calendar

Project Description for Google Calendar Feature #1: Find Meeting Rooms Feature #2: Show Busy Schedule Feature #3: Check if Meeting is Possible Feature #4: Schedule a New Meeting Feature #5: Find Common Meeting Times Feature #6: Find Two Sets of Consecutive Days Feature #7: Longest Busy Period What Did We Learn?DIY: Find Interval Sets DIY: Merge Intervals DIY: My Calendar DIY: Insert Interval DIY: Interval Lists Intersection DIY: Employee Free Time DIY: Find Two Non-Overlapping Subarrays Each with Target Sum DIY: Longest Consecutive Sequence

Stock Scraper

Project Description for Stock Scraper Feature #1: Traversing DOM Tree Feature #2: Locating Stock Data Feature #3: Traversing DOM Tree II Feature #4: Maximum Profit What Did We Learn?DIY: Binary Tree Level Order Traversal DIY: Lowest Common Ancestor of a Binary Tree DIY: Lowest Common Ancestor of a Binary Tree III DIY: Populating Next Right Pointers in Each Node DIY: Populating Next Right Pointers in Each Node II DIY: Maximum Subarray DIY: Best Time to Buy and Sell Stock

UBER

Project Description for Uber Feature #1: Select Closest Drivers Feature #2: Path Cost Feature #3: Plot and Select Path Feature #4: Fare in Words Feature #5: Uber Pool Feature #6: Longest Route Feature #7: Highest Rank Feature #8: Optimal Path What Did We Learn?DIY: K Closest Points to Origin DIY: Trapping Rainwater DIY: Evaluate Division DIY: Integer to English Words DIY: Random Pick with Weight DIY: Diameter of Binary Tree DIY: Kth Largest Element in an Array DIY: Minimum Path Sum

Amazon

Project Description for Amazon Feature #1: Suggest Items for Free Delivery Feature #2: Suggest Items for Special Offer Feature #3: Upselling Products Feature #4: Copy Product Data Feature #5: Order Processing Milestones Feature #6: Products Frequently Viewed Together Feature #7: Optimize Delivery Cost Feature #8: Merge Recommendations Feature #9: Products in Price Range Feature #10: Calculate the Total Cost of the Shopping Cart Items Feature #11: Ad Serving Feature #12: Warehouse and Drop Points Feature #13: Time-Based Item Price Store Feature #14: Find Similar Products What Did We Learn?DIY: Two Sum DIY: Three Sum DIY: 3Sum Closest DIY: Insert, Delete, and GetRandom in O(1)DIY: Insert Delete GetRandom O(1) - Duplicates Allowed DIY: Copy List with Random Pointer DIY: Find First and Last Position of an Element in Sorted Array DIY: Find All Anagrams in a String DIY: Random Pick Index DIY: Continuous Subarray Sum DIY: Accounts Merge DIY: Range Sum of BST DIY: Basic Calculator II DIY: Basic Calculator III DIY: Read N Characters Given Read4 II — Call Multiple Times DIY: Walls and Gates DIY: Time-Based Key-Value Store DIY: Intersection of Two Arrays

Zoom

Project Description for Zoom

Feature #1: Display Meeting Lobby

Feature #2: Serialize and Deserialize Participant Data

Feature #3: Meeting Activity

Feature #4: Validate Sorted Participants Data

Feature #5: Auto Rotate in Mobile Devices

What Did We Learn?

DIY: Binary Search Tree Iterator

DIY: Serialize and Deserialize Binary Tree

DIY: Jump Game IV

DIY: Validate the Binary Search Tree

DIY: Rotate Image

Plagiarism Checker

Project Description for Plagiarism Checker Feature #1: Possible Matches Feature #2: Return Match What Did We Learn?DIY: Number of Matching Subsequences DIY: Minimum Window Subsequence

Network

Project Description for Network Feature #1: Total Time Feature #2: TTL Expiry Feature #3: Minimum Hops Feature #4: Maximum Routers Feature #5: Update VLAN ID Feature #6: Transmission Error Feature #7: Divide Files Over the Network Feature #8: Maximum Clock Skew Feature #9: Update Configuration Feature #10: Minimum Variation Feature #11: Weighted Exponential Back-off Feature #12: Peak Signal Strength What Did We Learn?DIY: Time Needed to Inform All Employees DIY: All Nodes Distance K in Binary Tree DIY: Jump Game II DIY: Longest Increasing Path in a Matrix DIY: Flood Fill DIY: Valid Palindrome II DIY: Partition Labels DIY: Maximum Difference Between Node and Ancestor DIY: Rotting Oranges DIY: Longest Subarray With Absolute Diff Less Than Equal to Limit DIY: Add Two Numbers DIY: Add Two Numbers II DIY: Find Peak Element

Cyber Security

Project Description for Cyber Security Feature #1: Validate Packet Structure Feature #2: Verify Message Integrity Feature #3: Find Dictionary Feature #4: Ways to Decode Message Feature #5: Eligible Candidates What Did We Learn?DIY: UTF-8 Validation DIY: Verifying an Alien Dictionary DIY: Alien Dictionary DIY: Decode Ways DIY: Find K Closest Elements

Operating System

Project Description for Operating System Feature #1: Allocate Space Feature #2: Resume Process Feature #3: Schedule Processes Feature #4: Compress File Feature #5: Recover Files Feature #6: File Management System Feature #7: Serialize and Deserialize File System Feature #8: Compress File II Feature #9: File Search Feature #10: Decode a Message Feature #11: Directory Iterator Feature #12: Priority Validation Feature #13: Reverse Commands Feature #14: Releasing Process Lock Feature #15: Queue Reconstruction by Priority What Did We Learn?DIY: Subarray Sum Equals K DIY: Missing Element in a Sorted Array DIY: Course Schedule DIY: Course Schedule II DIY: Sequence Reconstruction DIY: Concatenated Words DIY: Minimum Remove to Make Valid Parentheses DIY: Design Add and Search Words Data Structure DIY: Serialize and Deserialize N-ary Tree DIY: String Compression DIY: Regular Expression Matching DIY: Wildcard Matching DIY: 24 Game DIY: Flatten Nested List Iterator DIY: Frog Jump DIY: Queue Reconstruction by Height DIY: Reverse Words in a String DIY: Single Element in a Sorted Array

Language Compiler

Project Description for Language Compiler Feature #1: Remove Comments Feature #2: Evaluate the Arithmetic Expression Feature #3: Loop Unrolling Feature #4: Optimization by Replacement Feature #5: Compilation Step Failure Feature #6: Most Common Token Feature #7: Exponentiation for Mobile Devices Feature #8: Divide in Power Save Mode Feature #9: Validate Program Brackets What Did We Learn?DIY: Count a Word in the Comments DIY: Basic Calculator DIY: Decoding a String DIY: Find and Replace in a String DIY: First Bad Version DIY: Nested List Weight Sum DIY: Most Common Word DIY: Pow(x, n)DIY: Divide Two Integers DIY: Valid Parentheses DIY: Valid Parenthesis String

Boggle

Project Description for Boggle Feature #1: Search for a Single Word in the Boggle Grid Feature #2: Search for Maximum Number of Words in the Boggle Grid What Did We Learn?DIY: Word Search I DIY: Word Search II

Scrabble 2.0

Project Description for Scrabble Feature #1: Minimum Moves Feature #2: Possible Results What Did We Learn?DIY: Word Ladder I DIY: Word Ladder II

Game

Project Description for Game Feature #1: Hand of Straights Feature #2: Maximum Points You Can Obtain from Cards Feature #3: Balloon Splash What Did We Learn?DIY: Divide Array in Sets of K Consecutive Numbers DIY: Find Maximum Sum from Either End of an Array DIY: Remove All Adjacent Duplicates In String DIY: Remove All Adjacent Duplicates in String II

Stocks

Project Description for Stocks Feature #1: Validate Price Feature #2: Settling Period Feature #3: Goals Fulfilled Feature #4: Milestone Reached Feature #5: Top Brokers Feature #6: Assign Transactions Feature #7: Process Transactions Feature #8: Find Intervals What Did We Learn?DIY: Valid Number DIY: Task Scheduler DIY: Split Array into Consecutive Subsequences DIY: Searching a 2D Matrix DIY: Top K Frequent Elements DIY: Reverse Nodes in k-Group DIY: Reverse Linked List II DIY: String to Integer (atoi)DIY: Daily Temperatures

Computational Biology

Project Description for Computational Biology Feature #1: Mutate DNA Feature #2: Detect Virus Feature #3: Locate Protein Feature #4: Identifying Proteins Feature #5: Mutating a Virus Feature #6: Identify a Species Feature #7: Detecting a Protein Feature #8: Similarity Measure Between DNA Samples Feature #9: Kth Missing Gene What Did We Learn?DIY: String Transforms into Another String DIY: Longest Substring with At Most K Distinct Characters DIY: Longest Palindromic Substring DIY: Valid Palindrome DIY: Next Permutation DIY: Longest Substring without Repeating Characters DIY: Palindrome Permutation DIY: Palindromic Substrings DIY: Edit Distance DIY: Kth Missing Positive Number

Cellular Operator(AT&T)

Project Description for Cellular Operator Feature #1: Determine Location Feature #2: Low Coverage Area Feature #3: Power Up the Station Feature #4: Query Peak Users Feature #5: Maximum Contiguous Area Feature #6: Densest Deployment Feature #7: Maximum Users Feature #8: Maximum Signal Strength What Did We Learn?DIY: Search a 2D Matrix II DIY: Largest Rectangle in Histogram DIY: Maximal rectangle DIY: Open Lock DIY: Range Sum Query 2D — Immutable DIY: Minimum Area Rectangle DIY: Sliding Window Maximum DIY: Max Area of an Island DIY: Max Consecutive Ones III DIY: Shortest Bridge

Twitter

Project Description for Twitter Feature #1: Add Likes Feature #2: Merge Tweets In Twitter Feed Feature #3: Identify Peak Interaction Times Feature #4: Split Users into Two Groups Feature #5: Drawing a Global Profile of Viral Tweets Feature #6: Incoming Tweets Predictor Feature #7: Trending Hashtags What Did We Learn?DIY: Add Binary DIY: Multiply Strings DIY: Merge Sorted Arrays DIY: Maximum Sum of Three Non-Overlapping Arrays DIY: Is Graph Bipartite?DIY: The Skyline Problem DIY: Moving Average from a Data Stream DIY: Find Duplicate Files in System

Trees

Invert Binary Tree Flip Equivalent Binary Trees Binary Tree Maximum Path Sum Binary Tree Zigzag Level Order Traversal Binary Tree Right Side View Binary Tree Vertical Order Traversal Boundary of Binary Tree Flatten Binary Tree to Linked List

Miscellaneous

Minimum Knight Moves Sparse Matrix Multiplication Design In-Memory File System Spiral Matrix Design Tic-Tac-Toe The Maze Restore IP Addresses Reconstruct Itinerary Text Justification Gas Station Strong Password Checker Sudoku Solver Pacific Atlantic Water Flow Angle Between the Hands of a Clock

Conclusion

Where to Go from Here?

DIY: Validate the Binary Search Tree

Solve the interview question "Validate the Binary Search Tree" in this lesson.

Problem statement

For this challenge, you are given an integer array. You have to implement the inorder_BST() function to ...

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