good!!

是字母就是（x+5）%26.非字母原样输出。
字符串以START开始END结束（即无需处理）测试以ENDOFINPUT结束

这是哪个OJ上的题目，格式要求很怪。

我在杭电里找到的

(x+5)对应的是加密，这个是解密，要想办法减5，或者加上21.

那就（x-5）%26

First, this is a Caesar problem, you should calculate the encoding function and decoding function by hand (or at least in your mind). Then, choose a language to solve it. Java or Matlab is preferred, C,C++.... well not so good for discrete math.
I got the encoding function E(y) is congruent x + 5 (mod 26)
      and the decoding function D(x) is congruent y - 5 (mod 26).
Transfer the decoding function to any compu-language u like. (the question only ask for from the un-readable code to human-readable words, so just use the decoding function).
The question's mathmatic part is pretty simple(A -> F is the easiest case). Also, the programming language is less than 50 lines of code. GOOD LUCK. (srry i was in lab cant type chinese) :)

nothing

[[it] 本帖最后由 prankmoon 于 2009-7-23 20:54 编辑 [/it]]