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How To Solve Informatics Olympiad?

International Olympiad in Informatics (IOI): What algorithms should I study for INOI?

  • INOI stands for Indian National Olympiad of Informatics. It's one of the rounds for selection of Indian IOI team. I want to know what topics of algorithms I need to know to solve INOI problems. For example I have heard that something named Network Flows doesn't come in IOI and INOI. Any other topics which don't come or come? I wish to study all the algorithms but lack of time won't allow me, thus I want to study those that come. Also, I have heard that there are few C++ techniques that eliminates the need of writing complete algorithms eg- not writing a code for sorting and directly using some predefined code in C++ that we can use. Can we use such things in INOI? Where can I learn to use such things? I know C++ and implementation and I can solve few codeforces problems which doesn't require algorithms or some simple DP.

  • Answer:

    Back in my time, I can tell you that logic with no knowledge of standard algorithms will be enough to clear you. I did INOI with coding up a buggy quicksort (the bug was with large input sets) and writing a recursion without DP (which would TLE for inputs having n>25 for sure). Not that much has changed since then if you ask me. Which brings me to the next point: The best way you have to clear the INOI is by writing correct code. Don't forget the above. Finally, it's definitely a good thing to learn early on, so that you start getting comfortable with implementations and algorithms. The material in is a good place. I will particularly recommend Topcoder's http://community.topcoder.com/tc?module=Static&d1=tutorials&d2=standardTemplateLibrary for the STL. That, and practice on Topcoder, Codeforces, and Codechef to keep yourself in shape.

Pradeep George Mathias at Quora Visit the source

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The following is the official syllabus for IOI : http://people.ksp.sk/~misof/ioi-syllabus/ioi-syllabus.pdf Good quality study material by organizers of INOI : http://www.iarcs.org.in/inoi/online-study-material/ And regarding implementing things in C++, the "C++ techniques" you are referring to is the C++ standard template library. And it is completely legal to use them. To figure out how to use those libraries, jut try Googling "<data structure name> C++ STL" and you should get good results. For example, "heap C++ STL" or "set C++ STL". Although, I think implementing each algorithm once will really improve your understanding of the same. And I doubt you can use the STL strategy for many problems. Hope that helps. Happy coding :)

Keshav Dhandhania

The most important algorithms for INOI , if frequency of occurrence in INOI is considered, are graph algorithms and the similarly the most important problem solving strategy is DP. If you have less time, you should focus on these two specially as at least one question from these two is definitely asked. Even if you solve one question completely, chances are you'll get selected. This year, I solved one problem completely which required deriving a recursive formula and implementing a DP and the other one partially, which involved implementing a modified Kadane's algorithm(I didn't knew this at the time of exam). A good resource for practising is USACO Training pages. PS: Don't consider me an expert. I'm just another naive coder.

Divyansh Shukla

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