Week 346 - (Magic)

3 files changed, 128 insertions, 0 deletions

diff --git a/challenge-346/peter-campbell-smith/blog.txt b/challenge-346/peter-campbell-smith/blog.txt
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+http://ccgi.campbellsmiths.force9.co.uk/challenge/346
diff --git a/challenge-346/peter-campbell-smith/perl/ch-1.pl b/challenge-346/peter-campbell-smith/perl/ch-1.pl
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+++ b/challenge-346/peter-campbell-smith/perl/ch-1.pl
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+#!/usr/bin/perl
+
+# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge
+
+use v5.26;    # The Weekly Challenge - 2025-11-03
+use utf8;     # Week 346 - task 1 - Longest parenthesis
+use warnings; # Peter Campbell Smith
+binmode STDOUT, ':utf8';
+use Encode;
+
+longest_parenthesis('(()())');
+longest_parenthesis(')()())');
+longest_parenthesis('((()))()(((()');
+longest_parenthesis('))))((()(');
+longest_parenthesis('()(()');
+longest_parenthesis('))');
+longest_parenthesis('()()()()()');
+longest_parenthesis(')))())))');
+
+sub longest_parenthesis {
+	
+	my (@parens, $best, $explain, $start, $i, $length, 
+		$height, @opens, $this, %previous);
+	
+	# initialise
+	@parens = split('', $_[0]);
+	@opens = ();
+	$best = $start = $height = 0;
+	$explain = '';
+
+	# loop over string
+	for $i (0 .. $#parens) {
+		$this = $parens[$i];
+		
+		# found ( - record as start
+		if ($this eq '(') {
+			push(@opens, $i);
+			$height ++;
+			
+		# found )
+		} elsif ($this eq ')' and $height > 0) {
+			$height --;
+			
+			# ( and ) match
+			unless ($height < 0) {
+				$start = pop(@opens);
+				
+				# check for this being the longest
+				$length = $i - $start + 1;
+				if (defined $previous{end} and $start == $previous{end} + 1) {
+					$length += $previous{length};
+					$start = $previous{start};
+				}
+				
+				# record info
+				if ($length >= $best) {
+					$explain = '' if $length > $best;
+					$best = $length;
+					$explain .= qq[($start .. $i), ];
+					%previous = (start => $start, length => $length, end => $i);
+				}
+			
+			# unmatched ) - forget all previous starts
+			} else {
+				@opens = ();
+				$start = $i + 1;
+			}
+		}		
+	}
+	
+	say qq[\nInput:  '$_[0]'];
+	say qq[Output: ] . ($best > 0 ? qq[$best at ] . substr($explain, 0, -2) : 'none');
+}
diff --git a/challenge-346/peter-campbell-smith/perl/ch-2.pl b/challenge-346/peter-campbell-smith/perl/ch-2.pl
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+++ b/challenge-346/peter-campbell-smith/perl/ch-2.pl
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+#!/usr/bin/perl
+
+# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge
+
+use v5.26;    # The Weekly Challenge - 2025-11-03
+use utf8;     # Week 346 - task 2 - Magic expression
+use warnings; # Peter Campbell Smith
+binmode STDOUT, ':utf8';
+use Encode;
+use Algorithm::Combinatorics 'variations_with_repetition';
+
+magic_expression(123, 6);
+magic_expression(105, 5);
+magic_expression(232, 8);
+magic_expression(1234, 10);
+magic_expression(13579, 115);
+magic_expression(314159265, 868140);
+
+sub magic_expression {
+	
+	my (@ints, $target, $gaps, @ops, $iterator, $p, $trial, $g, $value, $output);
+	
+	# initialise
+	@ints = split('', $_[0]);
+	$target = $_[1];
+	$gaps = $#ints;
+	@ops = (' + ', ' - ', ' * ', '');
+	$output = '';
+	
+	# loop over variations of @ops
+	$iterator = variations_with_repetition([0, 1, 2, 3], $gaps);
+	while ($p = $iterator->next) {
+		
+		# create string of digits with every perm of @ops
+		$trial = '';
+		for $g (0 .. $gaps - 1) {
+			$trial .= $ints[$g] . $ops[$p->[$g]];
+		}
+		$trial .= $ints[$gaps];
+		
+		# eliminate ones containing leadng 0s eg 05
+		next if $trial =~ m{( 0\d|\(0\d)};
+		
+		# evaluate the string and see if it matches $target
+		$value = eval($trial);
+		next unless $value == $target;
+		
+		# it does
+		$output .= qq[($trial), ];
+	}
+		
+	say qq[\nInput:  \$str = '$_[0]', \$target = $target];
+	say qq[Output: \$output = ] . ($output ? substr($output, 0, -2) : 'not possible');
+}