Maybe it sounds simple to computer scientists, I just want to backup some logical deduction of myself in NP-completeness proofs in case I will deal with such proofs in the future. In NP-completeness proof, we always want to find a polynomial-time reduction (transformation) from problem A to problem B, denoted as: We say that there …
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It’s a bit shame that I just start to learn music theory of guitar chords after FIVE years since I picked up guitar. In this post I will share how I have learned guitar chords from beginning. 1. know mappings from alphabets to do-rei-mi-fa-so-la-si C is DO, D is REI, E is MI, so …
You know, in latex you can type \neq to make an inequation symbol: `$latex \neq$` Of course, you don’t want to remember how to type in latex all symbols with backslash on them. So here is a general way to add backslash on any symbol in latex: add `\not` in front of a normal …
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Intuitively, Breadth-First Search (BFS) can find shortest distances from a source $latex s&s=4$ to any other reachable vertex. However, proving this intuition needs a bit hard work. After some searches, I found that there are two ideas to prove it. The two ideas both use induction to prove it. Both ideas require a bit long proof. …
WordPress really SUCK! It doesn´t provide a viable, simple and easy solution for export/import of your whole site. Here I am sharing how I managed to migrate my WordPress site from an old host to a new one. make sure Apache2, PHP, MySQL, and PHP MySQL extension work in perfect on your new host. Here …
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It again proved how silly WordPress is: I can’t find any theme with wide content area. Why do we have to waste almost a third of page area in EVERY WordPress theme? I read many articles about how to make custom CSS to widen the content column but no magic happened. So I decided to modify …
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After searching on the Internet for a whole day back in Spring break, I finally found one video that is not junk. Mate Desktop looks elegant. I am really pissed off however when I found I can’t change mouse primary button in Mate. God bless fake left-hand user.
Background In my memory, `sapply` is a function that takes a vector to consume and returns another vector as result. Today I am sharing a “bizarre” behavior of it. Later I will talk about the reason to account for this weird behavior. Details Let’s first look at the following line, from which I scratched …
背景 Git历史记录中，若不小心加入了较大的而无用的文件，很可能会让你的repository的size变得很大。Github和Bitbucket都分别对repository的大小做出了限制 （见https://help.github.com/articles/what-is-my-disk-quota/ 及https://confluence.atlassian.com/pages/viewpage.action;jsessionid=735235A3CE151FB6D4C518F3971FD524.node2?pageId=273877699）。那么如何在Git的历史记录中找出较大的文件并且删除它们呢？