Where to get a good problem with solution algorithms

Question

I know some system of online judgment of the algorithm, but some of them have an attached solution. In most cases, after I answer my own answer to this system, I see that other people's solution has less memory usage and a shorter processor cost, which after refactoring my code cannot be achieved. Are there any problems with elegant solutions? I want to read the solution to find where to fill in the blank. Thanks in advance!

Answer 1

TopCoder has many challenges and solutions made in contests.

Answer 2

Google Code. , - (, UVa, SPOJ) google .

Answer 3

FWIW, CodeChef . . .

Answer 4

http://refactormycode.com/ [deadlink] - , . . , Topcoder,