85 minutes C/C++ only.
I gave them a brute force algorithm then I got rejected two days later :/
Anyway the description is as bellow:

Minimum length of (-2) base integers.
Given an integer, it can be represented using (-2) base.

Example:
original | (-2) base
-2 | 10
4 | 100
-8 | 1000

Write a function that returns the (-2) base integer and the length of it must be the smallest of all possible representations.

vector<int> convert(int integer)

I can't remember the test case but one thing is that it's definitely not an easy or medium level question because it has so many pitfalls.

Hope it helps.

Related problems:

• https://leetcode.com/problems/convert-to-base-2/