Question

What would be an example of using recursion (with little explanation and/or code sample)?

Answer 1

Uses: Parsing; traversal; generating fractals; some forms of encryption

Examples: Towers of Hanoi; Fibonacci Seq; Subset generation (there are tons of examples, I can code a few of these for you if you want?)

Advantages: Simple; Intuitive for certain problems (e.g. Ackermann function, traversal)

Disadvantages: Slow (although you can implement any recursive solution using stacks); May result in stackoverflow exception

In case, anyone is wondering about encryption, here is a short explanation of Cipher Block Chaining Mode:

Chaining adds a feedback mechanism to the block cipher. Blocks are
first encrypted, and their results are then fed back into the
encryption of the next block. Each block thus modifies the encryption
of the next block.

In CBC, the plaintext is first encrypted, with the result stored in a
feedback register. Then the next plaintext is XORed with the contents
of the register. This becomes the next input of the encryption
routine. The resulting encryption is stored in the feedback register
again and the next plaintext is XORed with this. This process repeats
till the end of the message. For decryption, a block is decrypted
normally and stored in the feedback register- after the next block is
decrypted, it is XORed with the results of the feedback register and
so on.

[adapted from Bruce Shneier’s excellent book, Applied Cryptography]