I have been sharpening my algorithm skills since one year ago. First I solved all the problems on LeetCode, but then I found the problems in CodeForces, UVa, Topcoder etc. are much harder than those in LeetCode. So I started to try to solve the problems on those OJ. And sometimes I found that once I solved a problem, I could forget how I solved it after a few days. That's why I posted all my solutions as soon as I solved a problem for future respection.