Get Minimum Round Trip Cost (for E4)

Problem Overview

• Find the minimum round-trip flight cost given two arrays: departing[i] and returning[j], with the constraint j > i.
• Input: costs by time index for depart and return; Output: smallest possible sum; required time complexity O(n).
• Real-world context: choosing the cheapest outbound and return flights where return occurs after departure.
• This Meta interviews coding interview problem is a common interview question focused on cost optimization.