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Ask HN: Where to find programming challenges for sharpening algorithmic skills?

20 points by Fa773NM0nK ↗ HN
I am looking for a set of programming challenges that'll help sharpen my algorithmic skills.

I've worked a bit with CodeChef and SPOJ. Both have problems that test problem solving abilities of varied nature.

However, I am unable to decide which one to follow through with. So I decided to ask the community.

What resources would you suggest for improving my thinking/algorithmic skills? Something, that'll have problems spanning all the fundamental concepts.

I am a student of Computer Science Engineering, and I'm not new to programming or algorithms; though I'm a far cry from being an expert.

I had tried my hand at Project Euler too, but you can get through those problems with sub-optimal solutions. For eg. the first problem's solution can be arrived by at by using an O(1) algorithm, but the system would accept a solution generated using an O(n) algorithm too. That wouldn't motivate deep thinking. (http://projecteuler.net/problem=1)

12 comments

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pocha
Have you tried www.hackerrank.com ? I have not personally used it. Also, I am not a big fan of algorithmic problems either.
Fa773NM0nK
I've not tried hackerrank.

Will surely give it a whirl.

linux_devil
Both codechef and SPOJ are good enough , focusing on one will be a good strategy. You may give a try to interviewstreet as well. But like I said mastering problems on any one of the sites is sufficient .
tujv
I highly recommend the book "Programming Challenges" by Steven Skiena, used in conjunction with UVA Online Judge at http://onlinejudge.org.

Each challenge takes the form of a word problem. The solution can be coded in a few different languages and uploaded to the website.

The site imposes time limits when running the solution. When I've found that my solution works but is too slow, it has encouraged me to look for different data structures or algorithms.

I can't recommend it enough.

tim_hutton
Keep going with Project Euler. It's not long before the brute force approach stops working. On later problems you will find many ways to solve them but very few that return an answer in less than a week, say.
dagw
You can only brute force the first handful of Project Euler problems. You quickly hit problems where the difference between the right and wrong approach is seconds vs hours or days.
bjourne
Add solutions to problems at http://rosettacode.org. Even if your solution is suboptimal, someone is likely to come along and improve it. Or create a totally new problem and solve it in your language of choice.
brudgers
The Art of Computer Programming, Knuth.
WizzleKake
I can recommend Rosalind http://rosalind.info/problems/locations/

It has bioinformatics problems. They start really easy ("count the bases in a DNA sequence") and get progressively harder.

For each problem you get some sample data to work with. When you think you've figured it out, you can download a dataset to run your algorithm against, then upload the output to see if you are correct. There's a time limit for submission, and although you can keep re-trying, the data sets are different each time.

Check it out! Don't let the bioinformatics part throw you off.