Sites that give algorithmic coding problems

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.
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)
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bio informatics -
math related problems -
algorithm/programming problems -
user submitted problems (not really algorithmic tbh most of the time) - /r/dailyprogrammer
codegolf (solve problems in as few characters as possible) -
python stuff -

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

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

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