I don't think the ebook is available, or I would have had a free pirated version by now lol More on reddit.com

A lot of competitive programmers (eg. Errichto) recommend this book: https://cses.fi/book/book.pdf That being said, I tried competitive programming to prepare for interviews and found out it’s a huge waste of time if your primary goal is to ace interviews. You don’t want to spend time learning Euler’s totient function or convex hulls because they will never come up in an interview setting for a generalist software engineer. Focus on leetcode, study the solutions in the discussion section, be patient and consistent, and you will improve over time. The EPI book would be my recommendation. It is the right level for interview prep, not too easy not too hard. More on reddit.com

I searched prime to figure out how to lower run time of finding tons of prime, but didn't really get an answer. Sieve of Eratosthenes would still run time error. For example, find how many primes are in between 15353535 and 1247597239573. You guys know how to do this? This was a question in a past hackerrank contest More on reddit.com

Speaking from experience, you'll do well by learning Discrete Mathematics (Hash Tables, Sets, Graphs, Trees etc.), and lots of Number Theory (Combinatorics, The Chinese Remainder Theorem, The Pigeon-hole Principle et al). If nothing else, master Graphs & Trees. They will get you 70-80% of the way there. On a more practical level, download this worksheet - https://docs.google.com/spreadsheets/d/1iJZWP2nS_OB3kCTjq8L6TrJJ4o-5lhxDOyTaocSYc-k/edit#gid=84654839 , and work through level "A" in parallel with learning the relevant mathematics. Progress up the levels - B, C, etc. as you get better. Follow this guide if you want just one definitive resource to follow. Go through this free ebook - https://cses.fi/book/book.pdf , and have a look at the main topics that are needed for CP, including the mathematics. Research more on the topics mentioned or that you see in problems. Use this http://codeforces.com/problemset?order=BY_SOLVED_DESC and start solving problems, focusing on correctness first and then improving speed and accuracy. Note that some of the questions from this site may appear in the worksheet mentioned above. Always read the editorials even if you have solved the problem by yourself, from scratch (you can find that at the bottom lower right of the page of the problem statement). Use https://www.spoj.com/problems/classical/ for more practice (note that this site is not very reliable when it comes to the test cases, but it's okay for the most part). Finally, I would suggest registering and attending contests right from the start - you'll hardly be able to solve more than a single problem to begin with, but you'll improve, and again, always go through the editorials post every contest. Which sites for contests? Codeforces as above, CSAcademy, Atcoder.jp etc. Participate in as many contests as you can - that's the only way to improve. tl;dr: learn and improve via problem-solving and contests and picking up the relevant mathematics. If you want one book recommendation for Discrete Mathematics, Kolman & Busby is an approachable resource. For maths practice and improving problem solving, "Problem Solving through Recreational Mathematics" by Auerbach & Chein is excellent, but not very easy. Don't get overwhelmed. If nothing else, as before, start with the Worksheet and contests (and editorials, editorials, editorials!). Everything else will follow. Above all else, don't get burnt out, and enjoy yourself! Good luck! EDIT: https://chrome.google.com/webstore/detail/coders-calendar/bageaffklfkikjigoclfgengklfnidll?hl=en is also a good plugin to keep track of upcoming contests. More on reddit.com