Recent days. I accidentally read the book: Cracking the Coding Interview: 189 Programming Questions and Solutions. This is a pretty good book; books written on frequently asked questions in interviews, interview process of Yahoo, Google, Amazon, Facebook. There are lots of good programming questions in the book, I just share some of the questions I feel are simple and interesting. If you want to learn more, please find your own ebook.
Cracking the Coding Interview PDF download link