Reverse Without Built-Ins | Dataford Interview Questions

SentinelOne telemetry processing may require reversing a sequence before further analysis. Write a function that reverses either a string or a list without using built-in reverse functions, slicing-based reversal, or library helpers that directly reverse the input.

Return a new sequence in reverse order. The original list must remain unchanged. For a string, return a string. For a list, return a list containing the same elements in reverse order.

Formal Specification

Implement reverse_sequence(sequence), where sequence is either a string or a list of values. The function returns the same sequence type with its elements ordered from last to first. An empty input is valid.

Use a two-pointer approach that swaps elements from the outside toward the center. Do not call reverse(), reversed(), or use reverse slicing such as [::-1].

Constraints

0 <= len(sequence) <= 10^5
sequence is either a string or a list
List elements may be integers, strings, or other values
Do not use reverse(), reversed(), or reverse slicing
The original list must remain unchanged

Function Signature

def reverse_sequence(sequence):

Your question is Reverse Without Built-Ins. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem