Rujia Liu's Present 5

Hello, everyone! My name is Rujia Liu. I used to do a lot of problem solving and problemsetting, but after graduated from Tsinghua University, I'm spending more and more time on my company

(You may realized that the paragraph above is copied from the texts of my 3rd and 4th contest, but that's me, lazy me.)

This time, my contest is all about developing software's. Well, I know that it's very difficult to finish a good software within contest time, but I'm trying to allow the contestants to enjoy the happiness of coding, not just algorithms. As usual, don't hesitate to write emails to me (rujia.liu@gmail.com) during the contest for any reason (e.g. the problems are unclear to you, or you suspect that the judge data might be wrong). Please remember that my goal is to help you learn more, not prevent you from solving problems.

This contest is about software developing, so don't forget that you can always use google. I even gave some hints the problems that contain external resources for you to learn. So... try your best and solve these problems!

I know that some of these problems are very tricky or complex, so I decided to provide some additional data that make your life (a little bit) easier. You can download them on the contest website.

Thanks Mingjing Xiaoliu for problem G, and H, Yechen Li for problem B, Peichao Zhang for problem F, Zhuohua Chen for problem A, G and I, Feng Chen for problem J, Youzhi Bao for problem A, C, E, and the Mua series.

Problem D, F and H are adapted from previous Chinese Olympiad in Informatics contests, with test data greatly enhanced. Thanks for the authors of the original problems and reference materials (Yifei Zhang, Cailiang Liu, Shi Li, Rong Ge, Tiancheng Lou, Weidong Hu). And finally, the authors of the Lua programming language: that is my favorite embedded language.