[all] Formatting, missing comments in header, etc

10 files changed, 249 insertions, 203 deletions

diff --git a/005/ch1.pl b/005/ch1.pl
index 1c3436f..aa06105 100755
--- a/005/ch1.pl
+++ b/005/ch1.pl
@@ -1,37 +1,41 @@
 #!/usr/bin/env perl
+#
+# Write a program which prints out all anagrams for a given word. For more information about Anagram, please check this wikipedia page
+# (https://en.wikipedia.org/wiki/Anagram)
+################################################################################
 
 use strict;
 use warnings;
 
 sub anagrams {
-	# Tail-recursive with accumulator; iterate over the word accumulating the
-	# anagrams that can be formed with the already-seen characters
-	sub iter {
-		# @acc contains the already computed anagrams
-		my ($word, @acc) = @_;
-		if (length($word) == 0) {
-			# Finished consuming word -> return accumulator
-			return @acc;
-		} else {
-			# Split the current word: first letter vs the rest
-			my ($head, $tail) = $word =~ /^(.)(.*)$/;
-			@_ = $tail; # Next word will be the tail of the previous one
-			# Compute new anagrams by inserting the current letter in all the
-			# positions of the previous anagrams
-			foreach my $anagram (@acc) {
-				for (my $i = 0; $i <= length($anagram); $i++) {
-					push(@_, $anagram);
-					substr($_[-1], $i, 0) = $head;
-				}
-			}
-			goto &iter;
-		}
-	}
-	iter(shift, (""));
+    # Tail-recursive with accumulator; iterate over the word accumulating the
+    # anagrams that can be formed with the already-seen characters
+    sub iter {
+        # @acc contains the already computed anagrams
+        my ($word, @acc) = @_;
+        if (length($word) == 0) {
+            # Finished consuming word -> return accumulator
+            return @acc;
+        } else {
+            # Split the current word: first letter vs the rest
+            my ($head, $tail) = $word =~ /^(.)(.*)$/;
+            @_ = $tail; # Next word will be the tail of the previous one
+            # Compute new anagrams by inserting the current letter in all the
+            # positions of the previous anagrams
+            foreach my $anagram (@acc) {
+                for (my $i = 0; $i <= length($anagram); $i++) {
+                    push(@_, $anagram);
+                    substr($_[-1], $i, 0) = $head;
+                }
+            }
+            goto &iter;
+        }
+    }
+    iter(shift, (""));
 }
 
 for (@ARGV) {
-	for (anagrams($_)) {
-		print $_, "\n";
-	}
+    for (anagrams($_)) {
+        print $_, "\n";
+    }
 }
diff --git a/006/ch1.pl b/006/ch1.pl
index 5ec9203..bac675c 100755
--- a/006/ch1.pl
+++ b/006/ch1.pl
@@ -1,34 +1,39 @@
 #!/usr/bin/env perl
+#
+# Create a script which takes a list of numbers from command line and print the
+# same in the compact form. For example, if you pass “1,2,3,4,9,10,14,15,16”
+# then it should print the compact form like “1-4,9,10,14-16”
+################################################################################
 
 use strict;
 use warnings;
 
 sub compact {
-	my @ns = split(/,/, shift);
-	my $from = my $to = shift @ns; # The first interval is the first number
-	my @intervals;
+    my @ns = split(/,/, shift);
+    my $from = my $to = shift @ns; # The first interval is the first number
+    my @intervals;
 
-	# Store the current interval ($from, $to) and advance to the next one
-	my $save = sub {
-		push(@intervals, $from == $to ? $from : "$from-$to");
-		$from = $to = shift;
-	};
+    # Store the current interval ($from, $to) and advance to the next one
+    my $save = sub {
+        push(@intervals, $from == $to ? $from : "$from-$to");
+        $from = $to = shift;
+    };
 
-	# Iterate over the numbers, expanding the last interval or starting a new one
-	foreach my $n (@ns) {
-		if ($to == $n-1) {
-			$to = $n;
-		} else {
-			&$save($n);
-		}
-	}
+    # Iterate over the numbers, expanding the last interval or starting a new one
+    foreach my $n (@ns) {
+        if ($to == $n-1) {
+            $to = $n;
+        } else {
+            &$save($n);
+        }
+    }
 
-	# Store the last interval (except for empty input)
-	&$save if defined $to;
+    # Store the last interval (except for empty input)
+    &$save if defined $to;
 
-	return join(",", @intervals);
+    return join(",", @intervals);
 }
 
 foreach (@ARGV) {
-	print compact($_), "\n";
+    print compact($_), "\n";
 }
diff --git a/007/ch1.pl b/007/ch1.pl
index 8102da6..490ced4 100755
--- a/007/ch1.pl
+++ b/007/ch1.pl
@@ -1,4 +1,9 @@
 #!/usr/bin/env perl
+#
+# Print all the niven numbers from 0 to 50 inclusive, each on their own line. A
+# niven number is a non-negative number that is divisible by the sum of its
+# digits
+################################################################################
 
 use strict;
 use warnings;
diff --git a/008/ch1.pl b/008/ch1.pl
index 81d590c..bbd1893 100755
--- a/008/ch1.pl
+++ b/008/ch1.pl
@@ -1,10 +1,14 @@
 #!/usr/bin/env perl
+#
+# Write a script that computes the first five perfect numbers. A perfect number
+# is an integer that is the sum of its positive proper divisors (all divisors
+# except itself).
+# (https://en.wikipedia.org/wiki/Perfect_number)
+################################################################################
 
 use strict;
 use warnings;
 
-my @primes;
-
 sub perfect {
     my $sum = 0;
     my $n = shift;
diff --git a/009/ch1.pl b/009/ch1.pl
index e98223d..12147ce 100755
--- a/009/ch1.pl
+++ b/009/ch1.pl
@@ -1,4 +1,8 @@
 #!/usr/bin/env perl
+#
+# Write a script that finds the first square number that has at least 5 distinct
+# digits
+################################################################################
 
 use strict;
 use warnings;
diff --git a/009/ch2.pl b/009/ch2.pl
index 336dda0..d20def5 100755
--- a/009/ch2.pl
+++ b/009/ch2.pl
@@ -1,41 +1,53 @@
 #!/usr/bin/env perl
+#
+# Write a script to perform different types of ranking as described below:
+#
+# 1. Standard Ranking (1224): Items that compare equal receive the same ranking
+# number, and then a gap is left in the ranking numbers.
+# 2. Modified Ranking (1334): It is done by leaving the gaps in the ranking
+# numbers before the sets of equal-ranking items.
+# 3. Dense Ranking (1223): Items that compare equally receive the same ranking
+# number, and the next item(s) receive the immediately following ranking number.
+#
+# (https://en.wikipedia.org/wiki/Ranking)
+##############################################################################
 
 use strict;
 use warnings;
 
 sub rank {
-	my $rank_type = shift;
-	my @points = sort @_;
+    my $rank_type = shift;
+    my @points = sort @_;
 
-	my %ranks;
-	my $rank = $rank_type eq "modified" ? 0 : 1;
+    my %ranks;
+    my $rank = $rank_type eq "modified" ? 0 : 1;
 
-	my $interval_begin = 0;
-	my $i;
-	for ($i = 0; $i < @points; $i++) {
-		my $point = $points[$i];
-		if ($point != $points[$interval_begin]) {
-			my @points_to_add = @points[$interval_begin .. ($i-1)];
-			$rank += @points_to_add if $rank_type eq "modified";
-			$ranks{$rank} = \@points_to_add;
-			if ($rank_type eq "standard") {
-				$rank += @points_to_add;
-			} elsif ($rank_type eq "dense") {
-				$rank = $rank + 1;
-			}
-			$interval_begin = $i;
-		}
-	}
-	my @points_to_add = @points[$interval_begin .. ($i-1)];
-	$rank += @points_to_add if $rank_type eq "modified";
-	$ranks{$rank} = \@points_to_add;
-	return \%ranks;
+    my $interval_begin = 0;
+    my $i;
+    for ($i = 0; $i < @points; $i++) {
+        my $point = $points[$i];
+        if ($point != $points[$interval_begin]) {
+            my @points_to_add = @points[$interval_begin .. ($i-1)];
+            $rank += @points_to_add if $rank_type eq "modified";
+            $ranks{$rank} = \@points_to_add;
+            if ($rank_type eq "standard") {
+                $rank += @points_to_add;
+            } elsif ($rank_type eq "dense") {
+                $rank = $rank + 1;
+            }
+            $interval_begin = $i;
+        }
+    }
+    my @points_to_add = @points[$interval_begin .. ($i-1)];
+    $rank += @points_to_add if $rank_type eq "modified";
+    $ranks{$rank} = \@points_to_add;
+    return \%ranks;
 }
 
 # Get rank type and points as CLI arguments
 my $rank_type = shift || "";
 grep /^$rank_type$/, qw(modified standard dense)
-	or die "Usage: $0 {modified, standard, dense} rank1 rank2 ...";
+    or die "Usage: $0 {modified, standard, dense} rank1 rank2 ...";
 my @points = @ARGV;
 
 # Compute rankings
@@ -43,6 +55,6 @@ my $ranks = rank($rank_type, @points);
 
 # Display rankings
 for my $rank (sort (keys %$ranks)) {
-	my @positions = @{$ranks->{$rank}};
-	print "$rank. @positions\n";
+    my @positions = @{$ranks->{$rank}};
+    print "$rank. @positions\n";
 }
diff --git a/010/ch1.pl b/010/ch1.pl
index f2073ad..ad385d6 100755
--- a/010/ch1.pl
+++ b/010/ch1.pl
@@ -11,108 +11,108 @@ use warnings;
 
 # CLI usage
 sub usage {
-	print "$0 {-e ARABIC | -d ROMAN | --test}\n";
-	exit shift;
+    print "$0 {-e ARABIC | -d ROMAN | --test}\n";
+    exit shift;
 }
 usage -1 unless @ARGV > 0;
 if ($ARGV[0] eq "--test") {
-	test();
+    test();
 } else {
-	usage -1 unless @ARGV == 2;
-	if ($ARGV[0] eq "-d") {
-		print decode($ARGV[1]), "\n";
-	} elsif ($ARGV[0] eq "-e") {
-		print encode($ARGV[1]), "\n";
-	} else {
-		usage -1;
-	}
+    usage -1 unless @ARGV == 2;
+    if ($ARGV[0] eq "-d") {
+        print decode($ARGV[1]), "\n";
+    } elsif ($ARGV[0] eq "-e") {
+        print encode($ARGV[1]), "\n";
+    } else {
+        usage -1;
+    }
 }
 
 # roman -> arabic
 sub decode {
-	my @roman = split //, shift;
-
-	# Decimal value of each roman symbol
-	my %dec = (
-		M => 1000,
-		D =>  500,
-		C =>  100,
-		L =>   50,
-		X =>   10,
-		V =>    5,
-		I =>    1,
-	);
-	my $arabic = 0; # Return value
-
-	# Iterate over roman symbols
-	for (my $i = 0; $i < @roman; $i++) {
-		# Get current and next symbols
-		my ($currsym, $nextsym) = @roman[$i .. $i+1];
-		my $val = $dec{$currsym};
-
-		# Sub current value if next symbol is bigger; add it otherwise
-		if (defined $nextsym && $val < $dec{$nextsym}) {
-			$arabic -= $val;
-		} else {
-			$arabic += $val;
-		}
-	}
-
-	return $arabic;
+    my @roman = split //, shift;
+
+    # Decimal value of each roman symbol
+    my %dec = (
+        M => 1000,
+        D =>  500,
+        C =>  100,
+        L =>   50,
+        X =>   10,
+        V =>    5,
+        I =>    1,
+        );
+    my $arabic = 0; # Return value
+
+    # Iterate over roman symbols
+    for (my $i = 0; $i < @roman; $i++) {
+        # Get current and next symbols
+        my ($currsym, $nextsym) = @roman[$i .. $i+1];
+        my $val = $dec{$currsym};
+
+        # Sub current value if next symbol is bigger; add it otherwise
+        if (defined $nextsym && $val < $dec{$nextsym}) {
+            $arabic -= $val;
+        } else {
+            $arabic += $val;
+        }
+    }
+
+    return $arabic;
 }
 
 # arabic -> roman
 sub encode {
-	die "ERROR: Unable to encode numbers bigger than 9999" if $_[0] > 9999;
-
-	my @arabic = split //, shift;
-
-	my @symbols = ("I", "V", "X", "L", "C", "D", "M");
-	my @roman; # Return value (roman symbols)
-
-	# Iterate arabic digits from right to left (upward units)
-	for (my $i = $#arabic; $i >= 0; $i--) {
-		my $digit = $arabic[$i];
-
-		# Roman symbols corresponding to (1-5-10) given the current base
-		my ($one, $five, $ten) = @symbols;
-
-		# Roman symbols to add at the beginning of the current result
-		my @to_add;
-
-		# 4 and 9 are (5-1) and (10-1) respectively
-		if ($one ne "M" && ($digit == 4 || $digit == 9)) {
-			push @to_add, $one;
-			$digit++;
-		}
-
-		# Add the roman equivalents to the current digit
-		if ($one eq "M") {
-			# For 4000-9999, just add as much M's as needed
-			push @to_add, (map $one, (1..$digit));
-		} elsif ($digit == 10) {
-			push @to_add, $ten;
-		} elsif ($digit > 4) {
-			push @to_add, ($five, map $one, (6..$digit));
-		} elsif ($digit > 0) {
-			push @to_add, (map $one, (1..$digit));
-		}
-		unshift @roman, @to_add;
-
-		# For the next decimal, discard two roman symbols (one + five)
-		shift @symbols foreach (1..2);
-	}
-
-	return join "", @roman;
+    die "ERROR: Unable to encode numbers bigger than 9999" if $_[0] > 9999;
+
+    my @arabic = split //, shift;
+
+    my @symbols = ("I", "V", "X", "L", "C", "D", "M");
+    my @roman; # Return value (roman symbols)
+
+    # Iterate arabic digits from right to left (upward units)
+    for (my $i = $#arabic; $i >= 0; $i--) {
+        my $digit = $arabic[$i];
+
+        # Roman symbols corresponding to (1-5-10) given the current base
+        my ($one, $five, $ten) = @symbols;
+
+        # Roman symbols to add at the beginning of the current result
+        my @to_add;
+
+        # 4 and 9 are (5-1) and (10-1) respectively
+        if ($one ne "M" && ($digit == 4 || $digit == 9)) {
+            push @to_add, $one;
+            $digit++;
+        }
+
+        # Add the roman equivalents to the current digit
+        if ($one eq "M") {
+            # For 4000-9999, just add as much M's as needed
+            push @to_add, (map $one, (1..$digit));
+        } elsif ($digit == 10) {
+            push @to_add, $ten;
+        } elsif ($digit > 4) {
+            push @to_add, ($five, map $one, (6..$digit));
+        } elsif ($digit > 0) {
+            push @to_add, (map $one, (1..$digit));
+        }
+        unshift @roman, @to_add;
+
+        # For the next decimal, discard two roman symbols (one + five)
+        shift @symbols foreach (1..2);
+    }
+
+    return join "", @roman;
 }
 
 # Property:
 #   forall (x : Arabic). x == decode(encode(x))
 sub test {
-	foreach my $i (1..9999) {
-		my $roman = encode($i);
-		my $arabic = decode($roman);
-		die "ERROR: $i -> $roman -> $arabic" if $i != $arabic;
-	}
-	print "Test successful\n";
+    foreach my $i (1..9999) {
+        my $roman = encode($i);
+        my $arabic = decode($roman);
+        die "ERROR: $i -> $roman -> $arabic" if $i != $arabic;
+    }
+    print "Test successful\n";
 }
diff --git a/010/ch2.pl b/010/ch2.pl
index f0566df..a5a37f5 100755
--- a/010/ch2.pl
+++ b/010/ch2.pl
@@ -11,54 +11,54 @@ use warnings;
 use List::Util qw<max min>;
 
 sub jaro {
-	my @s1 = split //, shift;
-	my @s2 = split //, shift;
+    my @s1 = split //, shift;
+    my @s2 = split //, shift;
 
-	# Two chars in s1 and s2 match if they are not farther away than this number
-	my $match_dist = int(max (scalar @s1, scalar @s2) / 2)-1;
-	$match_dist = 0 if $match_dist < 0;
+    # Two chars in s1 and s2 match if they are not farther away than this number
+    my $match_dist = int(max (scalar @s1, scalar @s2) / 2)-1;
+    $match_dist = 0 if $match_dist < 0;
 
-	# Maps indices from s1 chars to matching s2 chars
-	my %matches;
+    # Maps indices from s1 chars to matching s2 chars
+    my %matches;
 
-	# Compute matches (fill the %matches hash)
-	S1:
-	foreach my $i (0 .. $#s1) {
-		foreach my $j ($i-min($i, $match_dist) .. min($i+$match_dist, $#s2)) {
-			# Skip s2 char if already matched
-			next if grep(/$j/, values %matches);
+    # Compute matches (fill the %matches hash)
+  S1:
+    foreach my $i (0 .. $#s1) {
+        foreach my $j ($i-min($i, $match_dist) .. min($i+$match_dist, $#s2)) {
+            # Skip s2 char if already matched
+            next if grep(/$j/, values %matches);
 
-			# If characters match, store match and advance to next char in s1
-			if ($s1[$i] eq $s2[$j]) {
-				$matches{$i} = $j;
-				next S1;
-			}
-		}
-	}
+            # If characters match, store match and advance to next char in s1
+            if ($s1[$i] eq $s2[$j]) {
+                $matches{$i} = $j;
+                next S1;
+            }
+        }
+  }
 
-	# Count number of matches and exit if 0
-	my $m = keys %matches;
-	return 0 if $m == 0;
+    # Count number of matches and exit if 0
+    my $m = keys %matches;
+    return 0 if $m == 0;
 
-	# Count transpositions
-	my $t = 0;
-	for my $k (keys %matches) {
-		$t += 1 if $k != $matches{$k};
-	}
+    # Count transpositions
+    my $t = 0;
+    for my $k (keys %matches) {
+        $t += 1 if $k != $matches{$k};
+    }
 
-	# Finally compute and return Jaro distance
-	return (($m/@s1) + ($m/@s2) + (($m-$t)/$m))/3;
+    # Finally compute and return Jaro distance
+    return (($m/@s1) + ($m/@s2) + (($m-$t)/$m))/3;
 }
 
 sub jaro_winkler {
-	my ($s1, $s2) = @_;
-	my $jarosim = jaro $s1, $s2;
-	my $l;
-	for ($l = 0; $l < length $s1; $l++) {
-		last if (substr($s1, $l, 1) ne (substr $s2, $l, 1));
-	}
-	my $p = 0.1;
-	return $jarosim + $l*$p*(1-$jarosim);
+    my ($s1, $s2) = @_;
+    my $jarosim = jaro $s1, $s2;
+    my $l;
+    for ($l = 0; $l < length $s1; $l++) {
+        last if (substr($s1, $l, 1) ne (substr $s2, $l, 1));
+    }
+    my $p = 0.1;
+    return $jarosim + $l*$p*(1-$jarosim);
 }
 
 die "Usage: $0 <s1> <s2>" unless @ARGV == 2;
diff --git a/012/ch2.pl b/012/ch2.pl
index ffd870c..3162569 100755
--- a/012/ch2.pl
+++ b/012/ch2.pl
@@ -1,4 +1,17 @@
 #!/usr/bin/env perl
+#
+# Write a script that finds the common directory path, given a collection of
+# paths and directory separator. For example, if the following paths are
+# supplied
+#
+# /a/b/c/d
+# /a/b/cd
+# /a/b/cc
+# /a/b/c/d/e
+#
+# and the path separator is /. Your script should return /a/b as common
+# directory path.
+################################################################################
 
 use strict;
 use warnings;
diff --git a/015/ch1.pl b/015/ch1.pl
index c6cc4db..b5ea460 100755
--- a/015/ch1.pl
+++ b/015/ch1.pl
@@ -7,8 +7,7 @@
 use strict;
 use warnings;
 
-use List::Util qw<any>;
-use List::Util qw<max>;
+use List::Util qw<any max>;
 
 my $LIMIT = 10;