给一个长度为的字符数组和一个长度为k的01数组req，根据要求编写折叠加密和解密的算法。

折叠加密方法举例：

reg[i]=0,表示从左到右折叠

a b c d e f g h  折叠加密后      d c b a

                             e f g h

d c b a        折叠加密后       f e

e f g h                         c d

                              b a

                              g h

reg[i]=1,表示从右到左折叠

a b c d e f g h  折叠加密后        h g f e

                               a b c d

f e           折叠加密后       h

c d                            a

b a                            d

g h                            e

                              f

                              c

                              b

                              g

好的，谢谢你！根据你说的对应关系我试试。