Re: Bracket Packing (#78)


#1

Here is my attempt. Go easy… my first quiz entry, and my first Ruby
script.

Regards,
Stu


class Packaging
attr_accessor :opening, :closing, :description

def initialize (o,c,desc)
@opening = o
@closing = c
@description = desc
end

def opp(v)
(v==@opening) ? @closing: @opening
end

def opening?(v)
@opening==v
end

def closing?(v)
@closing==v
end

def consistsOf?(v)
opening?(v) || closing?(v)
end
end

class PackagingPreProcessor
attr_accessor :packagingTypes

def initialize()
@types=[]
end

def addPackaging§
@types << p
end

def opening?©
@types.detect { |p| p.opening?© }
end

def closing?©
@types.detect { |p| p.closing?© }
end

def getPackagingType©
@types.detect { |p| p.consistsOf?© }
end

def processMessage(msg)
msg.final = msg.original
openStack=[]

aMsg=msg.original.split(//)

#Scan character by character for unbalanced brackets
aMsg.each_with_index do |c,i|

  # Push opening packaging type onto the stack
  if opening?(c)
    type=getPackagingType(c)
    openStack.push(type)
  end

  # Ensure closing brackets match the last opening bracket
  if closing?(c)

    currentPackagingTag=getPackagingType(c)

    expectedPackaging=openStack.pop

    if (expectedPackaging==nil)
      # We weren't expecting a close tag here.
      #
      #   Eg, {(B)(B)}]
      #               ^---- We a missing an opener for this
      #

      msg.final=currentPackagingTag.opening + msg.original
      return
    end

    if (currentPackagingTag != expectedPackaging)
      #
      # We have run into the wrong closing position,
      #
      # Two cases:
      #     We failed to open this position, eg : [B)], in which

case we will have a mismatch of ‘current’ brackets
# or
# There had been a subsequent position opened that needs
to be closed first - eg, [{B] - mismatch of expected brackets
#

      if (aMsg.select { |c| expectedPackaging.consistsOf?(c)

}.length % 2 != 0)
# need to insert the end braket of the expected packaging
msg.final=msg.original[0…(i-1)] + expectedPackaging.closing

  • msg.original[i…-1]
    return
    else
    # Insert an opening bracket to match the current closing
    bracket.
    msg.final = msg.original[0…(i-1)] +
    currentPackagingTag.opening + msg.original[i…-1]
    return
    end
    end
    end
    end

    if openStack.length!=0
    # Still have unclosed outer brackets (not picked up during stack
    matching)
    # EG, [{B}
    msg.final=msg.original + openStack.pop.closing
    return
    end

    end
    end

class Message
attr_reader :original
attr_accessor :final

def initialize(msg)
@original = msg
end

def valid?
@original==@final
end
end

#--------------------------

ppp=PackagingPreProcessor.new()

ppp.addPackaging(Packaging.new("(",")",“Soft Wrapping”))
ppp.addPackaging(Packaging.new("[","]",“Cardboard Box”))
ppp.addPackaging(Packaging.new("{","}",“Wooden Box”))

ARGF.each do |line|
msg=Message.new(line.chomp)
ppp.processMessage(msg)
print “\n”
print(msg.final)
print “\n”
end

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#2

:slight_smile: This is great :slight_smile: I enjoyed doing the quiz, and tried out a couple of
approaches: the stack based one (which seemed much more complex, and
even then didn’t cover all the cases), and this substitution on. Solving
the quiz was fun, but I picked up a lot of little things I didn’t know
along the way (either by bumping in to them, or looking at other
people’s solutions):

The pattern match variables $` and $’.
That you can use any start and end charater to deliminate a %w array
literal (or any of the related literals).
Having a test case in a script.
That the ruby command can be given params for the script itself.

Thank you community :slight_smile:

Cheers,
Benjohn

module SubValidator
module_function

def is_valid(s)
validate(s) rescue nil
end

def validate(s)
# Replace basic brackets in (valid) packaging, with packages.
s = s.gsub(/(B)|{B}|[B]/, ‘P’)

# Until the string is reduced to a single package...
while(s!='P')
  # Replace one of more packages in (valid) packing, with a single

package.
s, old_s = s.gsub(/(P+)|{P+}|[P+]/, ‘P’), s

  raise "Couldn't find any packages to package in '#{s}'." if 

s==old_s
end
true
end
end

require ‘test/unit’

class BracketTest < Test::Unit::TestCase
def test_validators
[SubValidator].each {|v| check_validator(v)}
end

def check_validator( validator )
# Simple cases that should pass.
valid_strings = %w<(B) {B} [B] ((B)) {(B)} ([{B}]) ((B)(B))
((((B)(B))(B))(B))>
valid_strings.each do |s|
assert_nothing_raised { validator.validate(s) }
end

# Simple cases that should fail.
invalid_strings = %w<() (b) [ B [B [} [B} } {{{{[B]}}} {{{{[B}}}

((B)B)> << ‘’
invalid_strings.each do |s|
assert_raises(RuntimeError) { validator.validate(s) }
end

# Try out a complex string - it should validate.
ok = "[({B}[B](B)[(B){[B][(B)]}]{B}{B})((B))]"
assert_nothing_raised{ validator.validate ok }

# Try dropping any of the chars - it should fail to vaildate.
ok.scan(/./) { assert_raises(RuntimeError) { validator.validate( $`
  • $’ ) } }

    Try adding any of the vaild chars at any point - it should fail to

validate.
%w<B ( ) { } [ ]>.each do |c|
ok.scan(//) { assert_raises(RuntimeError) { validator.validate( $`

  • c + $’ ) } }
    end
    end

    def test_is_valid
    assert_not_nil( SubValidator::is_valid( ‘(B)’ ) )
    assert_nil( SubValidator::is_valid( ‘’ ) )
    end
    end

if FILE == $0
if( ARGV[0] != ‘-t’ )
Test::Unit.run = false
exit( SubValidator::is_valid( ARGV[0] ) ? 0 : 1 )
else
ARGV.pop
end
end


#3

I’ve done a little refactor because I didn’t like the inline regular
expressions.

:slight_smile: Which makes me think that it’d be nice to have some extra methods in
Regexp that let you customise the special characters that it uses,
perhaps.

module SubValidator
module_function

def is_valid(s)
validate(s) rescue nil
end

def validate(s)
# Replace basic brackets in (valid) packaging, with packages.
s = s.gsub( packages_containing(‘B’), ‘P’ )

# Until the string is reduced to a single package...
while(s!='P')
  # Replace one of more packages in (valid) packing, with a single

package.
s, old_s = s.gsub( packages_containing(‘P+’), ‘P’ ), s

  raise "Couldn't find any packages to package in '#{s}'." if 

s==old_s
end
true
end

def packages_containing(filler_pattern)
Regexp.new( packings.map {|p| Regexp.escape§.gsub(‘x’,
filler_pattern)}.join(’|’) )
end

def packings
%w<(x) {x} [x]>
end
end

require ‘test/unit’

class BracketTest < Test::Unit::TestCase
def test_validators
[SubValidator].each {|v| check_validator(v)}
end

def check_validator( validator )
# Simple cases that should pass.
valid_strings = %w<(B) {B} [B] ((B)) {(B)} ([{B}]) ((B)(B))
((((B)(B))(B))(B))>
valid_strings.each do |s|
assert_nothing_raised { validator.validate(s) }
end

# Simple cases that should fail.
invalid_strings = %w<() (b) [ B [B [} [B} } {{{{[B]}}} {{{{[B}}}

((B)B)> << ‘’
invalid_strings.each do |s|
assert_raises(RuntimeError) { validator.validate(s) }
end

# Try out a complex string - it should validate.
ok = "[({B}[B](B)[(B){[B][(B)]}]{B}{B})((B))]"
assert_nothing_raised{ validator.validate ok }

# Try dropping any of the chars - it should fail to vaildate.
ok.scan(/./) { assert_raises(RuntimeError) { validator.validate( $`
  • $’ ) } }

    Try adding any of the vaild chars at any point - it should fail to

validate.
%w<B ( ) { } [ ]>.each do |c|
ok.scan(//) { assert_raises(RuntimeError) { validator.validate( $`

  • c + $’ ) } }
    end
    end

    def test_is_valid
    assert_not_nil( SubValidator::is_valid( ‘(B)’ ) )
    assert_nil( SubValidator::is_valid( ‘’ ) )
    end
    end

if FILE == $0
if( ARGV[0] != ‘-t’ )
Test::Unit.run = false
exit( SubValidator::is_valid( ARGV[0] ) ? 0 : 1 )
else
ARGV.pop
end
end