Find Encrypted Number

Problem Overview

• Given a sequence of digits, repeatedly sum adjacent digits and keep the rightmost digit of each sum until only two digits remain.
• Input: array numbers (2 <= n <= 5000, digits 0-9); Output: a 2-character string with the encrypted number.
• Context: encryption scheme inspired by a Pascal Triangle process for data security.
• From Amazon interviews; a coding interview problem and common interview question on arrays/strings.