Symmetric string mode
There are 12321 abcdedcba, and so on the form of a string, the requirements of generative rules or grammar or the use of a formal method of expression. Requirement
1 symmetric, variable length (or the form of a variable length is ignored by other conditions, the maximum length can be explained).
2 for ASCII code is tentatively scheduled for 32 to 126 characters
3 on both sides is monotonous, that is, for 12313431321 this string of characters, only 13431 parts
The 4 center is known.
That's what I needFormal string modeWhen I get a string dabcbadb and C is known to be the center, I can get this part of the abcba. This is the purpose, to mention the requirements can be discussed.
Do not understand the message is also welcome to exchange ah more urgent, there is nothing to say. I don't understand it, but I have to use it for a while. Currently read some of the books are in the form of expression in automaton's things as there are strings match, are relatively shallow...