TikTok User

Problem Overview

• Given array arr (length n) with some 0s, count the ways to replace 0s so the array is "good" (adjacent values differ by at most 1).
• Nonzero entries are fixed; replacements can be any integers; output the count modulo 1e9+7.
• Domain: assigning smoothly varying user numbers in a TikTok system.
• From TikTok interviews; a coding interview problem and common interview question on arrays/counting.