现有喜串定义如下。a 与b 互为喜串需满足以下两个条件之一： 1. a 和b 相同。 2. 将a 分成a1 与a2 两个等长串，b 分成b1 与b2 两个等长串，其子串需满足以下两个条件之一： a) a1与b1互为喜串且a2 与b2 互为喜串。 b) a1与b2互为喜串且a2 与b1 互为喜串。任务： 判断给定的两个串是否互为喜串-Hi existing string defined below. a and b mutually hi string must meet one of the following two conditions: 1. a and b are the same. 2. Place a a1 and a2 into two equal length strings, b b1 and b2 into two equal length strings, which substring must meet one of two conditions: a) a1 and a2 and b1 string hi to each other and b2 mutual hi string. b) a1 and a2 and b2 each other hi string hi string and b1 each other. Task: to determine whether a given two strings string hi to each other