Challenge 1: "Pythagoras Pie Puzzle, proposed by Jo Christian Oterhals.

At a party a pie is to be shared by 100 guest. The first guest gets 1%
of the pie, the second guest gets 2% of the remaining pie, the third
gets 3% of the remaining pie, the fourth gets 4% and so on.

Write a script that figures out which guest gets the largest piece of pie.
"

My notes:

Beautifully clearly described.  Sounds straightforward.


Challenge 2: "Write a script to validate a given bitcoin address. Most
Bitcoin addresses are 34 characters. They consist of random digits and
uppercase and lowercase letters, with the exception that the uppercase
letter O, uppercase letter I, lowercase letter l,
and the number 0 are never used to prevent visual ambiguity. A
bitcoin address encodes 25 bytes. The last four bytes are a checksum
check. They are the first four bytes of a double SHA-256 digest of the
previous 21 bytes. For more information, please refer wiki page. Here
are some valid bitcoin addresses:

1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2
3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy

My notes:

After reading several wiki pages, I think this (badly explained) question
means: decode type 1 or type 3 (not type bc1) Bitcoin addresses, which are
a base58check encoding of a 25 byte sequence, which itself comprises a 21
byte payload sequence followed by a 4-byte truncated sha256(sha256(payload)).

base58check itself is described here:
   https://en.bitcoin.it/wiki/Base58Check_encoding

However, there's some froody leading-zeroes shit, and the only really clear
specification of the whole process is a reference decoder implementation:
  http://lenschulwitz.com/b58/base58perl.txt
which is written in Perl 5!  so if the only way to understand exactly what
problem we're being asked to solve is to see a solution, in Perl 5, then
this seems like a completely pointless question.  So I took "Len
Schulwitz's" code above, and adapted it, which means that I didn't solve
this problem, in any real sense, myself!