diff options
| -rw-r--r-- | challenge-097/james-smith/perl/ch-2.pl | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl index 26bdfe22a1..9df291a034 100644 --- a/challenge-097/james-smith/perl/ch-2.pl +++ b/challenge-097/james-smith/perl/ch-2.pl @@ -8,22 +8,48 @@ use Test::More; is( min_flips('101100101',3), 1 ); is( min_flips('10110111', 4), 2 ); -is( min_flips('101100100',4), 1 ); +is( min_flips('101100100',3), 1 ); is( min_flips('0000000100100011010001010110011110001001101010111100110111101111',4), 32 ); +use Data::Dumper; + done_testing(); sub min_flips { - my( $str, $n, @parts ) = @_;; - my $min = length $str; - push @parts, substr $str,0,$n,'' while length $str; - foreach my $r (@parts) { - my $t = 0; - foreach my $s (@parts) { - $t += ($s^$r) =~ tr/\x01/\x01/; - } - $min = $t if $t < $min; - } - return $min; + ## Golf mode on... + return [ + map { local $/ = + local $\ = ( $_[0] ^ ( substr $_[0], $_, $_[1]) x (length($_[0])/$_[1]) ) =~ tr/\x01/\x01/, + !$_ || $_ < $/ ? $\ : $/, + } + map { $_*$_[1] } + 0 .. (length($_[0])/$_[1]-1) + ]->[-1]; + ## We could use variales here - but playing with localised special variables is fun! + ## $/ <- minimum value + ## $\ <- value for given chunk.... + ## + ## The inner map + range combination returns a list of ids of the form 0, $n, 2*$n until the + ## end of the array, we use this to chunk the array up for comparison + ## + ## Inside the end map - we first string "xor" the string with the repeated chunk of the array. + ## so e.g. for the first example this becomes: + ## '101100101' ^ '101'.'101'.'101' + ## '101100101' ^ '100'.'100'.'100' + ## '101100101' ^ '101'.'101'.'101' + ## if the symbols match you get a value \x00, when they don't match you get value \x01 + ## so we then count the \x01's using tr... and store in $\ + ## + ## Next if it is the first chunk OR the value of $\ is less than the current min ($/) + ## We set $/ to $\ otherwise we leave it as $/ + ## + ## The resultant array consists of the running minimum in the examples + ## for ex 1: it is [1,1,1] + ## for ex 2: it is [1,1] + ## for ex 3: it is [2,1,1] + ## + ## We need the last value of this so we wrap the list into an array ref and take the last element + ## + ## [ list... ]->[-1]; } |