Sites that give algorithmic coding problems

[jeb4]

Hey guys. For the guys who code, do you guys use any websites for practicing algorithmic coding problems? I'd like to know what people's thoughts/experiences were from them.

For me, a friend showed me this neat site for beginners called leetcode (yesterday actually). I had a certain expectation coming into this site because.. "beginners", but I got absolutely wrecked on the first "hard" problem. The solution concept wasn't that hard, but the actual implementation took hours for me because it was so susceptible to 1 off errors. Overall if this was given as an interview question, I probably would've failed it.

 

[billymills]

Like project euler? I remember doing a few of the problems there. Some were easy, some were pretty difficult.

I see what you mean by off-by-one errors.

I managed to beat the easiest hard problem I could find after about 15 minutes. My runtime was better than 0.51% of other people! (My slower solution timed out and didn't even get counted)

 

[Tomahawk]

bio informatics - rosalind.info
math related problems - projecteuler.net
algorithm/programming problems - codeabbey.com
user submitted problems (not really algorithmic tbh most of the time) - /r/dailyprogrammer
codegolf (solve problems in as few characters as possible) - codegolf.stackexchange.com
python stuff - checkio.org

 

[Minwu]

hacking - http://pmnb.net/

 

[Level 51]

I enjoy practicing on problems from past Google Code Jams (here); they come with a built-in judge system so you can check your output on the spot, and the puzzles take on a wide range of difficulties (Qualification Rounds feature entry-level puzzles while the Finals are obviously much harder).

 

[Kalawishis]

I suggest USACO, which my Computer Science UIL team is currently using to practice.

http://usaco.org/

Under the "training" bar, it has a various amount of coding problems that test all areas of algorithmic thinking.