字符串

Given two strings S​1​​ and S​2​​ , S=S​1​​ −S​2​​ is defined to be the remaining string after taking all the characters in S​2​​ from S​1​​ . Your task is simply to calculate S1​​​ −S​2​​ for any given strings.

Given a string, you are supposed to output the length of the longest symmetric sub-string.

Given a collection of number segments, you are supposed to recover the smallest number from them.

To prepare for PAT, the judge sometimes has to generate random passwords for the users. The problem is that there are always some confusing passwords since it is hard to distinguish 1 (one) from l (L in lowercase), or 0 (zero) from O (o in uppercase).