Write a script backup.sh that prompts the user a source folder and a destination folder and then copies recursively the source folder into the destination folder while preserving the nesting hierarchy of the source folder. Your script must validate the following two conditions before you create a duplicate copy of the source folder into the destination folder:

1) the source folder must exist, and

2) the destination folder does not exist. In addition, your script must seek at least a confirmation before creating a copy backup of the source folder in the destination folder.

Follow SCRIPTS 1 and 2 and write their equivalent in C++.