1. Reverse - Solution
  2. Factorial - Solution
  3. Longest Word - Solution
  4. Sum Nums - Solution
  5. Time Conversion - Solution
  6. Count Vowels - Solution
  7. Palindrome - Solution
  8. Nearby AZ - Solution
  9. Two Sum - Solution
  10. Is Power of 2? - Solution
  11. Third Greatest - Solution
  12. Most Common Letter - Solution
  13. Dasherize Number - Solution
  14. Capitalize Words - Solution
  15. Scramble String - Solution
  16. Is Prime? - Solution
  17. Nth Prime - Solution
  18. Longest Palindrome - Solution
  19. Greatest Common Factor - Solution
  20. Caesar Cipher - Solution
  21. Number of Repeated Letters - Solution



These questions are meant to prepare you for the coding challenge. You should read each question and try to solve them for yourself. Solutions are provided, look at those after making your attempt at the problem. Make sure you understand the solutions.

We've noted a difficulty level for each problem. The easy ones are a little easier than the problems you'll see on the challenge, the medium ones are a good proxy for the difficulty of the challenge, and the hard ones are generally harder than those you'll encounter on the challenge.

Run the file; if any "false" is output, then your program contains an error.

If you would like to review the Introduction to Programming Minibook, a recap of the various topics are available here: Introduction To Programming Summary.

Setup for Downloads

We strongly recommend you use Cloud9 ( to do the downloaded practice problems. See our setup instructions for instructions on how to use Cloud9.