matching parens

gistfile1.txt

# Task: write a function to determine if a string is
# 'balanced'. Balanced means that opening and closing
# brackets match each other in the proper order. Other
# characters are possible and should be handled. The 
# possible characters for balancing are {}, (), and []
 
# Example Input:
 
# '{}' -> True
# '{[]}' -> True
# '{5}' -> True
# '{[}' -> False
# '[A]{}d()' -> True
# 'a' -> True
# 'a}' -> False
# '([)]' -> False
# '{' -> False
 
# ((({{{{{[[[[(sdfklxlcdfja)]]]]}}}}})))
 
MATCHES = {'{' => '}', '[' => ']', '(' => ')'}
 
def balanced?(input)  
  a = input.chars.map.with_index.inject([]) { |current_open, c|
    c_val, c_index = c
    if MATCHES.keys.include?(c_val)
      current_open << c_val
    elsif MATCHES.values.include?(c_val)
      should_match = current_open.pop
      if MATCHES[should_match] == c_val
        current_open
      else
        msg = "FAILED at index #{c_index} with character #{c_val}"
        p msg
        [msg]
      end
    end    
  } 
  a.empty?
end

def should actual, expected
  if actual != expected
    puts "No! Got #{actual} instead of #{expected}"
  else
    puts "good"
  end
end


def bah 
  (0..1000000).map {|i| Random.rand(2) == 0 ? MATCHES.keys.sample : MATCHES.values.sample}.join 
end

should(balanced?(bah), true)

should(balanced?('{}'), true)
should(balanced?('{[]}'), true)
should(balanced?('([)]'), false)
  should(balanced?('[]]'), false)
  should(balanced?('[[]'), false)