Stable online question bank with reputation

Stable online question bank with reputation:

http://acm.timus.ru/ URAL

http://uva.onlinejudge.org/ UVA

http://acm.sgu.ru/index.php SGU

http://www.spoj.pl/ SPOJ - Poland's famous OJ, there are many good questions/ series, the disadvantage is that the machine is too slow

http://poj.org/ POJ --Hokkaido University

http://acm.hdu.edu.cn/ HDU - Hang Dian

http://ace.delos.com/usacogate USACO - Algorithm entry-level training questions (with algorithm explanation)

http://livearchive.onlinejudge.org/index.php ACM/ICPC Zhenti

http://oj.tsinsen.com/ Seio Orange OJ

http://acm.hust.edu.cn/vjudge/toIndex.action vjudge - A collection of major OJs

http://projecteuler.net/ Very loving math/algorithm question bank

 

Online algorithm competition website (also available as a question bank):

http://community.topcoder.com/tc Topcoder

http://codeforces.com/ Codeforces

http://www.codechef.com/ Codechef

http://main.edu.pl/en POI and other competitions

http://ace.delos.com/contestgate USACO Monthly Contest

http://code.google.com/codejam Google Code Jam