diff options
| -rw-r--r-- | challenge-017/duncan-c-white/README | 70 | ||||
| -rwxr-xr-x | challenge-017/duncan-c-white/perl5/ch-1.pl | 54 | ||||
| -rwxr-xr-x | challenge-017/duncan-c-white/perl5/ch-2.pl | 73 |
3 files changed, 161 insertions, 36 deletions
diff --git a/challenge-017/duncan-c-white/README b/challenge-017/duncan-c-white/README index e1b76f9a4c..37c8c6c8c7 100644 --- a/challenge-017/duncan-c-white/README +++ b/challenge-017/duncan-c-white/README @@ -1,45 +1,43 @@ -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. +Challenge 1: "Create a script to demonstrate Ackermann function. The +Ackermann function is defined as below, m and n are positive number: + + A(m, n) = n + 1 if m = 0 + A(m, n) = A(m - 1, 1) if m > 0 and n = 0 + A(m, n) = A(m - 1, A(m, n - 1)) if m > 0 and n > 0 + +eg. A(1, 2) = A(0, A(1, 1)) + = A(0, A(0, A(1, 0))) + = A(0, A(0, A(0, 1))) + = A(0, A(0, 2)) + = A(0, 3) + = 4 " My notes: -Beautifully clearly described. Sounds straightforward. +Clearly described. I seem to recall that the Ackermann function is +tremendously inefficient to calculate recursively, but that memoization +really helps. So, before writing a line of code, I think "use Memoize" +is going to help.. -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: +Challenge 2: "Create a script to parse URL and print the components of +URL. According to the Wiki page https://en.wikipedia.org/wiki/URL, the URL +syntax is as below: -1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2 -3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy + scheme:[//[userinfo@]host[:port]]path[?query][#fragment] -My notes: +eg. jdbc://user:password@localhost:3306/pwc?profile=true#h1 + + scheme: jdbc + userinfo: user:password + host: localhost + port: 3306 + path: /pwc + query: profile=true + fragment: h1 -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! +My notes: sounds pretty trivial for regexes, if the lexical syntax of +each component is defined clearly. Ok, reading the above wiki page +doesn't make it 100% clear, but let's hack it up, that's probably good +enough for most cases. diff --git a/challenge-017/duncan-c-white/perl5/ch-1.pl b/challenge-017/duncan-c-white/perl5/ch-1.pl new file mode 100755 index 0000000000..d48f37aca6 --- /dev/null +++ b/challenge-017/duncan-c-white/perl5/ch-1.pl @@ -0,0 +1,54 @@ +#!/usr/bin/perl +# +# Challenge 1: "Create a script to demonstrate Ackermann function. The +# Ackermann function is defined as below, m and n are positive number: +# +# A(m, n) = n + 1 if m = 0 +# A(m, n) = A(m - 1, 1) if m > 0 and n = 0 +# A(m, n) = A(m - 1, A(m, n - 1)) if m > 0 and n > 0 +# +# eg. A(1, 2) = A(0, A(1, 1)) +# = A(0, A(0, A(1, 0))) +# = A(0, A(0, A(0, 1))) +# = A(0, A(0, 2)) +# = A(0, 3) +# = 4 +# " +# +# My notes: +# +# Clearly described. I seem to recall that the Ackermann function is +# tremendously inefficient to calculate recursively, but that memoization +# really helps. So, before writing a line of code, I think "use Memoize" +# is going to help.. + +use strict; +use warnings; +use Function::Parameters; +use Data::Dumper; +use Memoize; + +die "Usage: ch-1.pl M N\n" unless @ARGV==2; +my $m = shift // 3; +my $n = shift // 100; + +# +# my $amn = A($m,$n); +# Calculate Ackermann's function for m,n>=0 +# A(m, n) = n + 1 if m = 0 +# A(m, n) = A(m - 1, 1) if m > 0 and n = 0 +# A(m, n) = A(m - 1, A(m, n - 1)) if m > 0 and n > 0 +# +fun A( $m, $n ) +{ + die "A($m,$n): m $m must be positive\n" if $m<0; + die "A($m,$n): n $n must be positive\n" if $n<0; + return $n+1 if $m == 0; + return A($m-1,1) if $m>0 && $n==0; + return A($m - 1, A($m, $n - 1)); +} + +memoize("A"); + +my $amn = A($m,$n); +print "A($m,$n) = $amn\n"; diff --git a/challenge-017/duncan-c-white/perl5/ch-2.pl b/challenge-017/duncan-c-white/perl5/ch-2.pl new file mode 100755 index 0000000000..0fc5a6da02 --- /dev/null +++ b/challenge-017/duncan-c-white/perl5/ch-2.pl @@ -0,0 +1,73 @@ +#!/usr/bin/perl + +# Challenge 2: "Create a script to parse URL and print the components of +# URL. According to the Wiki page https://en.wikipedia.org/wiki/URL, the URL +# syntax is as below: +# +# scheme:[//[userinfo@]host[:port]]path[?query][#fragment] +# +# eg. jdbc://user:password@localhost:3306/pwc?profile=true#h1 +# +# scheme: jdbc +# userinfo: user:password +# host: localhost +# port: 3306 +# path: /pwc +# query: profile=true +# fragment: h1 +# +# My notes: sounds pretty trivial for regexes, if the lexical syntax of +# each component is defined clearly. Ok, reading the above wiki page +# doesn't make it 100% clear, but let's hack it up, that's probably good +# enough for most cases. + +use strict; +use warnings; +use Function::Parameters; +use Data::Dumper; + +# +# my %info = parse_url($url); +# Parse URL $url. Return a hash of the pieces. If parsing +# fails, return an empty hash. +# scheme:[//[userinfo@]host[:port]]path[?query][#fragment] +# eg. jdbc://user:password@localhost:3306/pwc?profile=true#h1 +# +# parses to: +# scheme: jdbc +# userinfo: user:password +# host: localhost +# port: 3306 +# path: /pwc +# query: profile=true +# fragment: h1 +# +fun parse_url( $url ) +{ + $url =~ s/^([^:]+):// || return (); + + my %hash; + $hash{scheme} = $1; + if( $url =~ s|^//|| ) + { + $hash{userinfo} = $1 if $url =~ s|^(.+)@||; + return () unless $url =~ s|^([\w\.]+)||; + $hash{host} = $1; + $hash{port} = $1 if $url =~ s/^:(\d+)//; + $hash{fragment} = $1 if $url =~ s/#([^#]+)$//; + $hash{query} = $1 if $url =~ s/\?([^\?]+)$//; + $hash{path} = $url; + } + return %hash; +} + + + +#die "Usage: ch-2.pl URL*\n"; +push @ARGV, 'jdbc://user:password@localhost:3306/pwc?profile=true#h1' + unless @ARGV; +foreach my $url (@ARGV) +{ + my %info = parse_url($url); + print "$url:\n". Dumper(\%info); +} |