Two friends have been using instant messenger and have also been watching too many spy movies. They are afraid that people will be able to listen in on their conversation, so they use steganography to hide what they are talking about. The friends send each other YouTube links that follow this pattern:
https://www.youtube.com/watch?v=UYU8Q3
This looks like any normal YouTube link to the untrained eye, but the text after the “v=” is actually an encoded message. Your job is to write a program that will decode a conversation encoded using these YouTube links. The encoding is done using the following table:
Every character in normal text is split into two encoded characters as follows:
1. Find the ASCII value of the character (for example, the letter h has an ASCII value of 104, or 01101000).
2. Use the integer value of the first 4 bits to get the first encoded character (for h, the first 4 bits are 0110, or 6, which maps to U from the table).
3. Do the same for the second 4 bits (for h, the second 4 bits are 1000, or 8, which maps to Y from the table).
4. Put these encoded characters together and repeat the process for each character in the string you are encoding (so h would map to UY).
Your program should reverse this process to find the actual text from the encoded link parameters.