找出两个字符串的最长公共子串。

给出一个字符串，请删除该字符串的前导空格和尾随空格，中间的空格若多余1个删减到1个。

我是个菜鸟，但软件会是我终生的事业~我有信心学好它，希望站长通融-Two strings to find the longest common sub-string. Given a string, remove the string leading spaces and trailing spaces, if the extra spaces in the middle of a cut to one. I was a rookie, but the software will be my lifelong career ~ and I am confident to learn it, and hope that owners accommodation