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diff --git a/challenge-166/james-smith/README.md b/challenge-166/james-smith/README.md index b653ba22ba..222ff79205 100644 --- a/challenge-166/james-smith/README.md +++ b/challenge-166/james-smith/README.md @@ -96,5 +96,207 @@ If we include the g->9 mapping we can have: ``` glossologists 0x 0000 91055 0109 1575 ( 2,551,232,066,033,013) ``` -# Challenge 2 - Z-diff +# Challenge 2 - k-diff +## The solution + +I approached this in a few different ways: + +### Getting the filenames... + +We can: + 1) Cheat - and create a hash of arrays; + 2) Use `opendir`/`readdir`/`closedir`; + 3) Use `blob '*/*'`; + 4) Use `<*/*>`. + +Each have advantages/disadvantages: + + * the first doesn't require us to create files on disk for testing; + * 2 allows you to find hidden file names but then you have to be careful with `.` & `..`. You have to join directory and filename to get the path + * 3 & 4 are essentially the same and get all "folders/entries". You have to split the path to get the directory and filename. + +The simplest approach is to use 3/4. + +```perl + my %directories; + for my $path ( sort blob '*/*' ) { + my( $dir, $file ) = split m{/}, $path; + push @{ $directories{$dir} }, -d $path ? "$file/" : $file; + } +``` + +### Finding a complete list of different filenames + +```perl + my @paths = sort keys %directories; + my %filename_counts; + for my $path ( @paths ) { + $filename_counts{ $_ }++ for @{$directories{ $path }}; + } +``` + +### Build templates for printing page horizontal line, sprintf table of heading/contents + +```perl + my $HORIZONTAL_LINE = join '-' x ( $length+2 ), ('+') x (1+@paths); + my $TEMPLATE = '|' . " %-${length}s |" x @paths; + + say $HORIZONTAL_LINE; + say sprintf $TEMPLATE, @paths; + say $HORIZONTAL_LINE; +``` + +### Workout what to print and printing + +``perl + ## map({$u{$F=$_}<@p?sprintf$T,map{($d{$_}[0]//'')ne$F?'': + ## shift@{$d{$_}}}@p:map{shift@{$d{$_}};()}@p}sort keys%u) + for my $filename ( sort keys %filename_counts ) { + if( $filename_counts{ $filename } == @paths ) { + shift @{$_} for values %directories; + next; + } + my @columns; + for (@paths) { + if( @{$directories{$_}} && $directories{$_}[0] eq $filename ) { + push @columns, shift @{$directories{$_}}; + } else { + push @columns, ''; + } + } + say sprintf $TEMPLATE, @columns; + } +``` + +## Just a minor block at the end +say $1 +## The full code (with comments) + +```perl +sub z_diff { + + ## Declare variables + + ## my($l,%d,$F,@p,%u,$T,$H)=0; + my( $length, %directories, %filename_counts )=0; + + ## Read all sub-directories containing files and store + ## in data structure as a hash of ordered arrays + ## For directories add a trailing slash... + + ## (@_=split/\//),push@{$d{$_[0]}},-d$_?"$_[1]/":$_[1]for sort<*/*>; + for my $pat ( sort blob '*/*' ) { + my( $dir, $file ) = split m{/}, $path; + push @{ $directories{$dir} }, -d $path ? "$file/" : $file; + } + + ## Get out an ordered list of directories... + + ## $u{$_}++for map{@{$d{$_}}}@p=sort keys%d; + my @paths = sort keys %directories; + + ## Find the length of the longest directory name, and + ## keep a record of the number of times each filename + ## has been seen (also gives list of all unique filenames) + + for my $path ( @paths ) { + $filename_counts{ $_ }++ for @{$directories{$path}}; + } + + ## Now find the length of the longest filename or directory name + ## This gives us the column widths for the pretty display... + + ## (length$_>$l)&&($l=length$_)for@p,keys%u; + for ( @paths, keys %filename_counts ) { + $length = length $_ if length $_ > $length; + } + + ## Generate the ASCII code for a horizontal bar in the table + ## and a template for sprintf for the rows of the table + + my $HORIZONTAL_LINE = join '-' x ( $length+2 ), ('+') x (1+@paths); + my $TEMPLATE = '|' . " %-${length}s |" x @paths; + + ## Draw the header {directory names} of the table.... + + ## say for$H=join('-'x($l+2),('+')x(1+@p)), + ## sprintf($T='|'." %-${l}s |"x@p,@p),$H, + say $HORIZONTAL_LINE; + say sprintf $TEMPLATE, @paths; + say $HORIZONTAL_LINE; + + ## Now draw the body - we loop through each of the unique filenames + ## and see whether it is in all 4 columns (in which case we skip) + ## otherwise we look to see which entries are present in each + ## directory and show those.... + + ## map({$u{$F=$_}<@p?sprintf$T,map{($d{$_}[0]//'')ne$F?'': + ## shift@{$d{$_}}}@p:map{shift@{$d{$_}};()}@p}sort keys%u) + for my $filename ( sort keys %filename_counts ) { + + ## If we have seen the file in all directories - we remove + ## it from all directory lists {and do nothing} + + if( $filename_counts{ $filename } == @paths ) { + shift @{$_} for values %directories; + next; + } + + ## If we haven't we loop through the rows if + ## the first entry is the file then we push it + ## on the list to print {and remove it from the directory list} + ## if not we just push an empty string to the + ## list + + my @columns; + for (@paths) { + if( @{$directories{$_}} && $directories{$_}[0] eq $filename ) { + push @columns, shift @{$directories{$_}}; + } else { + push @columns, ''; + } + } + say sprintf $TEMPLATE, @columns; + } + + ## Finally print out the bottom line + + ## $H + say $HORIZONTAL_LINE; +} +``` +## Obfurscated/Golf code... + +I started with a "simple" compact version of the code and then came +discussions with Eliza on the Perl Programmers Facebook group and things +slowly got smaller. A few bytes at a time... + +```perl +sub z{my($l,$F,%d,%u,$T,$H)=0;(@_=split'/'),push@{$d{$_[0]}},-d?"$_[1]/":$_[1] +for<*/*>;$u{$_}++for map{@{$d{$_}}}my@p=sort keys%d;$l<length?$l=length:1for@p, +@_=keys%u;say for$H=join('-'x($l+2),('+')x(1+@p)),sprintf($T="| %-${l}s "x@p.'|' +,@p),$H,map({$u{$F=$_}<@p?sprintf$T,map{($d{$_}[0]//'')ne$F?'':shift@{$d{$_}}}@p +:map{shift@{$d{$_}};()}@p}sort@_),$H} +``` + +**or** if we "allow" return characters inside strings - this is 351 bytes of +perly goodness... + +```perl +sub x{my($l,$F,%d,%u,$T,$H)=0;(@_=split'/'),push@{$d{$_[0]}},-d?"$_[1]/":$_[1] +for<*/*>;$u{$_}++for map{@{$d{$_}}}my@p=sort keys%d;$l<length?$l=length:1for@p, +@_=keys%u;say$H=join('-'x($l+2),('+')x@p,'+ +'),sprintf($T="| %-${l}s "x@p.'| +',@p),$H,map({$u{$F=$_}<@p?sprintf$T,map{($d{$_}[0]//'')ne$F?'':shift@{$d{$_}} +}@p:map{shift@{$d{$_}};()}@p}sort@_),$H} +``` + +**Notes** + - Where we use `$_` there are numerous function calls which use this when no + parameter is passed - in this case `length`, `split`, `-d`. + - When a "string" starts with a number than has a letter in it treats it as if + to add a space between the number and the rest of the string so we can rewrite + `1 for $condition` as `1for$condition`. + - we don't need to do `sort blob '*/*'` or `sort <*/*>` as for all "current" + versions of Perl we can assume that perl does this for us. |