You are to generate codes consisting of four letters, using the letters A, B, C and D. The rule is that, in each code, at least two letters that stand side by side should be the same. Applying this rule, how many different codes can you generate?
Examples: AAAA, CBBD, CCAA, DBBB.
The Prize for This Question: USB Flash Drive
Send your answer to email@example.com by 3 a.m. on November 30, or visit ieee.bilkent.edu.tr/zeka to submit your answer online, and get a chance to win the prize!
This question was prepared by Emrehan Halıcı, president of the Turkey Intelligence Foundation, for Bilkent IEEE.