The Elevator Trace

A medium Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain

Python

Difficulty

medium

Seniority

junior, mid

Problem

We need to simulate a sequential traversal of a nested data structure. Given a list of lists, return all elements visited first forward through every inner list left to right, then backward through the same lists right to left. Return the complete traversal sequence as a flat list.

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