Link: /question/25574458/ answer/31kloc-0/75374.
Source: Zhihu.
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-Welcome to PKU JudgeOnline, Judge Peking University Online. The topics above POJ are a bit old, but the advantages are that there are many people doing it, many classic algorithm questions and many problem-solving reports, which are suitable for getting started.
-ZOJ:: Online judge of Zhejiang University homepage. ZOJ is not used much, but there are several experiences that seem to be ok and worth a try.
-Welcome to Hangzhou Dianzi University Online Judge OJ. In recent years, Hangdian OJ has replaced POJ and become the most mainstream OJ in China. With rich topics and reasonable difficulty gradient, it is widely favored by universities all over the country. Every year, large and small competitions are held in OJ of Hangdian, and last year's Asian online competition was also held on it. This shows its position in the eyes of ACMer in China. Because of this, there are also many hdu problem-solving reports on the Internet, which are suitable for personal advanced training.
-Valladolid Football Club University Online Judge. It is the oldest and most famous online judge in the world. The question bank has detailed classification, such as the title of the World Finals, the title of Liu Rujia and so on. The types of topics are very wide. Most of the topics are difficult and suitable for beginners to hone their programming.
-Timus Online Judge Ural is a Russian online question bank. Compared with some OJ in China, the questions inside are quite difficult. The old members of our school's training team like to give the questions here to the new members, which shows that it has a certain leading role.
-Sphere Online Referee (SPOJ) SPOJ is one of the best online referees in Poland, with a harmonious interface and a variety of topics. It is suitable for players with a certain foundation to practice, and it is also a good platform for masters to improve their abilities. Legend has it that the architectural leader who ruled the world finished painting this OJ? (Correction: SGU is completed by the building leader, thank you.
Kang Connor
For more information, please refer to the blog: introduction to SPOJ-Seamount.
-USACO is the official competition website of American middle school students and a famous online question bank in the United States, which is an Olympic competition specially prepared for informatics players; The problem-solving method simulates the official competition, and adopts the evaluation method of standard evaluation machine, file input and output and direct submission of program source files; The website has a comprehensive training topic and is an indispensable website for learning informatics. Every year, NOI and NOIP will mention the above topics; Each problem is accompanied by a detailed solution, which can check the test data and running results, facilitate debugging, find errors and correct them.
The hierarchical structure of chapter by chapter is adopted, from easy to difficult, and the combination of imparting knowledge and practicing programming must be completed in turn to avoid the behavior of picking only simple topics; Each chapter is like a competition tutorial book, which forms a distinct knowledge structure, which is beneficial for beginners and experts of OI to gradually improve their level, fully learn all aspects of informatics and avoid bias. (Source: usaco_ Baidu Encyclopedia)
-Sara tov state university:: it was always 404 before going to SGU, so I dare not post it. Since the pro test can be put on, let's show it to everyone. This was painted by a real architect, OJ. Why did the building leader brush this OJ instead of another OJ in this answer? Because this OJ is really suitable for improving the level, it should be as difficult as Urals and SPOJ. Besides, I don't know much about it. In my mind, SGU, Urals and Spoy are all suitable for regionals. After graduation, I want to go to top companies such as Google to attend ACMer/Coder training. There is not much difference between them.
-Codeforces Codefores is an algorithm competition website in Russia, which was founded and maintained by Saratov State University. Codeforces mainly emphasizes algorithm competition, and there are regular online competitions every 1 week, and its question bank is also accumulated from the topics of each competition. Compared with the OJ with the question bank as the core, the algorithm competition of Codeforces is more suitable for training one's improvisation and programming ability under pressure.
HUSTOJ Huazhong University of Science and Technology Online Judge. HustOJ, like other mainstream OJ, also has a rich question bank. But its main use is that it provides such a thing called vjudge, which is a virtual judge. Through vjudge, you can directly extract topics from major OJs, including but not limited to all OJs mentioned above, and use these topics to build your own competition. It is very suitable for special training, daily training and friends to play together.
-LeetCode Online Judge Unlike many OJs, LeetCode is an OJ (LEETCode OJ is a platform for preparing technical coding interviews), mainly for interviewers. There are not many topics above. At present, there are only 152 topics, many of which are interview topics of many large companies. Questions are basic, and complicated algorithms are not examined. Many of them are the application of basic knowledge, and the difficulty is equivalent to topcoder div 1 250 or code forces div1a. If you want to practice programming basics or prepare for company interviews, I strongly recommend this OJ (thank you, roommate/training team god /CMU vice president).
@ Peng Yun
Students provide an introduction to Leetcode (11/2015 Update: My roommate accepted google's offer and stopped going to CMU).