online judge

An online judge is an online system to test programs in programming contests. They are also used to practice for such contests.

The system can compile and execute your code, and test your code with pre-constructed data. Submitted code may be run with restrictions, including time limit, memory limit, security restriction and so on. The output of the code will be captured by the system, and compared with the standard output. The system will then return the result.

When mistakes were found in a standard output, the submission will be unsuccessful. You must correct any errors in the code, and resubmit for re-judgement.

• read algorithm first!
• https://en.wikipedia.org/wiki/Competitive_programming

International Olympiad in Informatics (IOI)

• OI-Public-Library, OI essays and learning materials
• Wiki for OI / ICPC （某大型游戏线上攻略，内含炫酷算术魔法） https://oi-wiki.org
  • OI Wiki 致力于成为一个免费开放且持续更新的知识整合站点，大家可以在这里获取关于 编程竞赛 (competitive programming) 有趣又实用的知识，我们为大家准备了竞赛中的基础知识、常见题型、解题思路以及常用工具等内容，帮助大家更快速深入地学习编程竞赛。
• shareOI 算法竞赛课件分享

International Collegiate Programming Contest (ICPC)

• Stanford ACM-ICPC, This is a repository for the Stanford ACM-ICPC teams. It currently hosts (a) the team notebook, and (b) complete lecture slides for CS 97SI.
  The team notebook is compiled from codes written by previous Stanford team members and coaches.
• http://web.mit.edu/~ecprice/acm/notebook.pdf
• ACM Cheat Sheet
• ACM-ICPC Algorithms, Algorithms used in Competitive Programming
• ACM-ICPC Preparation, This program has been developed to learn Algorithms for use in Competitive Prorgamming

LeetCode

• LeetCode Animation All in One: Demonstrate all the questions on LeetCode in the form of animation.（用动画的形式呈现解LeetCode题目的思路）
• labuladong 的算法小抄: Crack LeetCode, not only how, but also why.
• LeetCode Solutions: A Record of My Problem Solving Journey
• 算法模板，最科学的刷题方式，最快速的刷题路径，你值得拥有~
• 熟能生巧 – 刷题的一些技巧的经验之谈

answers

• Complete solutions to LeetCode, LCOF and LCCI problems, updated daily
• LeetCode-Go, LeetCode Cookbook
• LeetCode In Action - Python Solutions

Project Euler

PARI/GP

• PARI/GP is a widely used computer algebra system designed for fast computations in number theory (factorizations, algebraic number theory, elliptic curves, modular forms, L functions...), but also contains a large number of other useful functions to compute with mathematical entities such as matrices, polynomials, power series, algebraic numbers etc., and a lot of transcendental functions. PARI is also available as a C library to allow for faster computations.
  Originally developed by Henri Cohen and his co-workers (Université Bordeaux I, France), PARI is now under the GPL and maintained by Karim Belabas with the help of many volunteer contributors.
• PARI is a C library, allowing fast computations.
• gp is an easy-to-use interactive shell giving access to the PARI functions.
• GP is the name of gp's scripting language.
• gp2c, the GP-to-C compiler, combines the best of both worlds by compiling GP scripts to the C language and transparently loading the resulting functions into gp. (gp2c-compiled scripts will typically run 3 or 4 times faster.) gp2c currently only understands a subset of the GP language.

OpenSource OJ

• zoj: Zhejiang University Online Judge - An online judge which allows people to solve algorithm problems online. http://acm.zju.edu.cn/
• Ejudge programming contest management system https://ejudge.ru
• NOJ's another online judge platform, stands for NJUPT Online Judge. It's written in PHP, GO, Python and other function-supporting languages and supports both online judges and virtual judges, we called it mixed judge. https://acm.njupt.edu.cn/
• hustoj Popular Open Source Online Judge based on PHP/C++/MySQL/Linux for ACM/ICPC and NOIP training, with easy installation. ??OJ?? http://www.hustoj.com/?cat=2
• vj4: The online judge service with millions of submissions, since 2005. https://vijos.org