Nice. That first one is a personal favorite. Do you do "competitive programming"? You might like it. There's contests of various flavors out there to get a bun

Nice. That first one is a personal favorite. Do you do "competitive programming"? You might like it. There's contests of various flavors out there to get a bunch of problems from. Random recommendation: "Looking for a Challenge", a _beautiful_ in every way book of problems. Seriously check it out. Can almost guarantee you'll love it judging from those problems you linked. Google Foobar is fun if you can get your way in. The codejam problems are nice (skip kickstarter mostly). codechef.com and codeforces.com have generally good problems (and fun contests if you're into that aspect).