bearzx's blog

Why does CODEFORCES not support LISP ?
By bearzx, 12 years ago, In English

Solving easy problems on online judge website is a good way to learn a new programming language. As LISP is a popular functional programming language, I wonder why do we can't submit source code written by LISP, while we can submit source code written by some other functional languages like Haskell, Scala or OCaml. Wish someone can explain this.

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Werid results about O2 optimization
By bearzx, 12 years ago, In English

Yesterday when I was attending the CodeForces#100, I met a werid problem.


It was Problem A, I wrote my code, submitted, and passed the pretest, as usual. After the system test, I found that my code failed at test 9, it is:

Input: 2 1000 500
Output: NO
Answer: YES
status no. : 1011828

However, when I tested the data on my PC, I noticed that I' ve passed the test. My classmates told me that it might be the reason of O2 optimization of g++, because I don' t add that option on my PC, while CodeForces do. And Later on I submitted again with the MS Visual C++, this time my code was accepted(see status no. : 1010135), interesting, huh?

And something more interesting, if I add some "cout" before a statement(for debugging), I' ll pass the test in custom test:

See the status no. : 1011863
In this situation, I just add an cout << "" before I make my desicion.

And if I remove the cout << "":

I think this kind of results might have something with the O2 optimization, as the optimization may reduce the orders when it is compiling the source code.

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