Custom Number Theory Problemset on Codeforces

I put together a "mashup" (custom collection of problems) focusing on Number Theory. It has a variety of problems that illustrate some number theory techniques and concepts useful to competitive programming, from a difficulty level of 800 (Beginner) to 2300 (Master-level). I encourage you to check out the problems on your own & try to solve them before watching, though it should be instructive & interesting either way. :) In this stream, I go through all the problems, explanation/motivation of the solutions, and implementations. My blog post: https://codeforces.com/blog/entry/85475 Link to the mashup (all problems, only viewable with a Codeforces account): https://codeforces.com/contestInvitation/8305134301b2607eaa233fc638ac5fbf91a5c82e The original problem links (viewable without a Codeforces account): A: https://codeforces.com/contest/472/problem/A B: https://codeforces.com/contest/876/problem/B C: https://codeforces.com/contest/1266/problem/C D: https://codeforces.com/contest/1242/problem/A E: https://codeforces.com/contest/1349/problem/A F: https://codeforces.com/contest/1110/problem/C G: https://codeforces.com/contest/1345/problem/C H: https://codeforces.com/contest/1295/problem/D I: https://codeforces.com/contest/893/problem/E J: https://codeforces.com/contest/1229/problem/B K: https://codeforces.com/contest/1182/problem/E L: https://codeforces.com/contest/1139/problem/D 0:00 Intro 7:49 Problem A (Design Tutorial: Learn from Math) 14:02 Problem B (Divisibility of Differences) 23:15 Problem C (Diverse Matrix) 47:18 Problem D (Tile Painting) 1:17:59 Problem E (Orac and LCM) 1:41:37 Problem F (Meaningless Operations) 2:01:21 Problem G (Hilbert's Hotel) 2:09:00 Problem H (Same GCDs) 2:20:48 Problem I (Counting Arrays) 2:31:09 Problem J (Kamil and Making a Stream) 2:42:13 Problem K (Product Oriented Recurrence) 3:14:38 Problem L (Steps to One) 4:04:25 Chatting