Nice coding questions:

How to reverse a link list (constraint: do not allocate any memory)?
How to remove every n node in the link list (modulo N) in a circular fashion? (What data structure is needed?)
How do you implement a memory manager (to provide service for malloc and free)?
How do you test for palindrome?
How do you check the longest length of a palindrome in a given string?

Given a list of path names, write an algorithm to reconstruct it using File APIs of your OS for a particular file types in those paths.

e.g.
name: Color Pics/Red/002redapples3.jpg
name: Color Pics/Red/002redwagonplane2.jpg
name: Audio/Word/ALIEN.mp3
name: Audio/Spelled/A-L-I-E-N.mp3
name: Audio/Word/APPLE.mp3
name: Audio/Spelled/A-P-P-L-E.mp3
name: Audio/Question/AWhatColorPants.mp3
name: Color Pics/Black/city-night.jpg
name: Conclusion01.mp3
name: Conclusion02.mp3

Only pick out the path with Audio and with mp3 files in it and reconstruct it.