Programming exercises

So right now I have nothing I need to code for myself, or at least nothing I'd be ABLE to code for myself, but I still want to improve the quality of my code/get better/learn more.

Does anyone know of a website with programming exercises of beginner-intermediate level for Sepples and/or Java that would actually interest me?

I googled around a little and most of the exercises there were shitty university assignments.

>>19
The time complexity of a decision problem is given as the time complexity of the best algorithm to solve it on a deterministic Touring machine. It is written as an order of an expression, e.g. O(x²).
If the expression is a polynomial, the problem is in P and often it's cool. When the expression is exponential, like in O(2^x), it's almost always not cool and the problem is in EXPTIME.
If a problem can be solved in polynomial time on a nondeterministic Touring machine, it's in NP. If a problem in NP has the property that all other problems in NP can be Karp reduced to it, then it's in NP-complete. A consequence of this is that if one problem in NP-C is in P, every problem in NP is in P.

Currently, we know that P ⊆ NP ⊆ EXPTIME and that P ≠ EXPTIME. The million dollar question is whether P = NP, NP = EXPTIME or neither.