Data Structures & Algorithms: Binary Search

Part 4 — the grand finale of the DSA series. Binary search is the algorithm hiding behind your phone's contact search, dictionary lookups, database indexes, and so much more. In this video, we build it from scratch in C#, trace it by hand, derive the math behind O(log n), and play "guess my number" to feel the algorithm in your own head.

If you've watched Parts 1–3, this is where everything comes together — arrays, linear search, and Big O all reinforce one beautiful algorithm.

📚 WHAT YOU'LL LEARN
• Why binary search requires sorted data (and what happens when it isn't)
• The three-pointer pattern: lo, hi, mid
• Why we write mid = lo + (hi - lo) / 2 (the real-world overflow bug)
• Why the equals sign matters
• The math behind O(log n) — derived, not memorized
• When to use linear vs binary (decision tree)

🔢 CHAPTERS
0:00 The phone book intuition
2:11 "Guess my number" — feeling the algorithm
5:18 The algorithm — three pointers explained
8:27 C# implementation & the overflow gotcha
10:50 Live demo: watching the range collapse
12:50 Tracing it by hand (again)
15:07 Why O(log n) — the math, derived from scratch
17:36 Linear vs Binary: when to use which
19:29 Decision tree for when to use Linear or Binary search
21:12 Series recap & what's next in the channel

🎯 SERIES PLAYLIST
This is Part 4 of 4 in my CS 101 series on Searching Algorithms:
▶️ Part 1 · Introduction & Arrays https://youtu.be/biCWGeXfMdY
▶️ Part 2 · Linear Search https://youtu.be/RxQgKlZ9BmE
▶️ Part 3 · Big O Notation https://youtu.be/8MiD0ME14kY
▶️ Part 4 · Binary Search ← you are here
📋 Full Playlist: https://www.youtube.com/playlist?list=PL6hgydTWOldzerQSQrNdyDlRRC2qiZL4Q

👤 WHO THIS IS FOR
CS students who want to write binary search correctly (off-by-one bugs love this algorithm), interview prep for FAANG and other tech roles, and self-learners ready to graduate from linear search.

💡 PREREQUISITES
All three previous parts. Especially Part 3 (Big O) — you'll need to understand O(log n) to appreciate why binary search is special.

🏁 SERIES COMPLETE
That's the full series! You now have a real foundation in arrays, searching, and algorithm analysis. Next on the channel: linked lists, stacks & queues, and recursion — make sure you're subscribed so you don't miss them.

💬 LEAVE A COMMENT
Which algorithm clicked best for you? Were there any moments where the math made sense for the first time? I read every comment.

#BinarySearch #Algorithms #DataStructures #CSharp #LogN #DSA #CS101 #ComputerScience #CodingInterview #LearnToCode #Programming #AlgorithmsExplained #DataStructuresAndAlgorithms #SoftwareEngineering #DivideAndConquer

Видео Data Structures & Algorithms: Binary Search канала nyrri