braces.rb

def braces(expresion)
  if expresion.length % 2 != 0
    puts '0'
    return
  end

  opening = [ '(', '[', '{']
  closing = [ ')', ']', '}']
  stack = []

  for i in 0..expresion.length - 1
    if opening.include? expresion[i]
      stack << expresion[i]
    elsif  closing.include? expresion[i]
      if stack.empty? or not pair?(stack.last, expresion[i])
        puts '0'
        break
      else
        stack.pop
      end
    end
  end

  puts '1' if stack.empty?
end

def pair?(open_exp, last_exp)
  opening = { '(' => 1, '[' => 2, '{' => 3 }
  closing = { ')' => 1, ']' => 2, '}' => 3 }

  index = opening[open_exp]
  last_exp == closing.key(index)
end

def analize(expresions)
  expresions.each do |exp|
    braces(exp)
  end
end


#analize([')(){}'])

#analize(['{()()}', '()'])

analize([ ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]', ')(){}', '[]({})', '([])', '{(){}}', '([)]' ])

palindrome.rb

def palindrome words
	words.each do |word_separate|
		valido = false
		permutations = word_separate.split(//).permutation.to_a
		
		permutations.each do |word|
			the_word = word.join
			if the_word == the_word.reverse
				puts the_word
				valido = true
				break # cuando lo encuentra		
			end
		end
		puts -1 if valido == false
	end
end


words = ["cecarar", "civic", "agwewq","falso","chicharito","penal","tirado"]
palindrome words

version02.rb

def palindrome words
  words.each do |word_separate|
    valido = false   
    word_separate.split(//).permutation.to_a.collect do |p|
      if p.join == p.join.reverse
        puts p.join
        valido = true
        break # cuando lo encuentra
      end
    end
    puts -1 if valido == false
  end
end

version3.rb

def palindrome words
  return false if words.length >= 1000 # max 1000 word in the list

  words.each do |word|
    if canRearrangeToPalindrome(word)
      compare = word.split(//)
      if compare == compare.reverse
        puts compare.join
      else
        rearrange(word)
      end
    else
      puts -1
    end
  end
  return
end

def rearrange(word)
  for i in 0..word.length - 1

    if i == word.length - 1
      # busqueda en el centro
      if word[0] == word[word.length - 1]
        #puts "BUSQUEDA CENTRAL"
        for j in 0..word.length - 2
          mid_temp = word[j+1]
          word[j+1] = word[j+2]
          word[j+2] = mid_temp
          compare = word.split(//)
          if compare == compare.reverse
            puts compare.join
            return true
          end
        end
      else
        return true if rearrange(word)
      end
    end

    tmp = word[i]
    word[i] = word[i + 1]
    word[i + 1] = tmp
    compare = word.split(//)

    if compare == compare.reverse
      puts compare.join
      return true
    end
  end
  return false
end

def canRearrangeToPalindrome(str)
  return false if str.length >= 1000 # max 1000 letters in a word
  letter_counts = {}
  palindromo_sum = 0

  for i in 0..str.length - 1
    letter = str[i]
    letter_counts[letter] = letter_counts[letter] || 0
    letter_counts[letter] += 1
  end

  letter_counts.each_key do |key|
    palindromo_sum += letter_counts[key] % 2
  end

  return palindromo_sum < 2;
end


palindrome [ "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb", "bb", "dbd", "ivcci", "oyotta", "cecarar", "bbb", "babbb"]


# http://codereview.stackexchange.com/questions/77511/check-if-string-can-be-rearranged-into-a-palindrome

Challenge 2: Palindromes
A palindrome is a word that reads the same backward as forward. For instance "civic" or "deed" are palindromes while "toyota" is not.
Given a list of words
Your task is to
write a function that rearranges their letters so that they become palindromes
for example, having the sequence “cecarar” we can rearrange the letters and obtain “racecar” which is a palindrome
print to the standard output (stdout) a single line containing one palindrome that can be obtained from the initial word by rearranging its letters or -1 if it’s not possible to obtain a palindrome (for each of the given words)
please note that the palindromes don't have to be necessarily real words from the English dictionary (e.g. dbd is a valid palindrome word)
Note that your function will receive the following arguments:
words
which is an array of strings giving the words that need to have their letters rearranged to obtain palindromes
Data constraints
the number of words that need to br rearranged will not exceed 1000
the maximum length of any of the words will not exceed 1000 characters
all words will contain only lowercase English letters (a-z)
Efficiency constraints
your function is expected to print the requested result and return in less than 2 seconds
Example
Input Output
words: [“ivcci”, “oyotta”, “cecarar”, "bbb", "babbb"]
civic
-1
racecar
bbb
bbabb

Challenge 3: Braces
Given an array of strings containing three types of braces: round (), square [] and curly {}
Your task is to
write a function that checks whether the braces in each string are correctly matched
prints 1 to standard output (stdout) if the braces in each string are matched and 0 if they're not (one result per line)
Note that your function will receive the following arguments:
expressions
which is an array of strings containing braces
Data constraints
the length of the array will not exceed 100
the length of any string will not exceed 5000
Efficiency constraints
your function is expected to print the result in less than 2 seconds

Challenge 1: Snake
Given a square matrix of integer numbers
Your task is to
write a function that prints the matrix to the standard output (stdout) on a single line starting in the upper-left corner and continuing clockwise, in circles, from exterior towards interior.
Note that your function will receive the following arguments:
matrix
which is an array of integers giving the matrix as follows. The first width elements in the array represent the first line of the matrix, the next width elements represent the second line of the matrix and so on.
width
which is an integer value giving the width of the square matrix
Data constraints
the width value will not exceed 250
all the elements in the matrix are integer numbers in the following range [1, 231 -1
Efficiency constraints
your function is expected to print the result in less than 2 seconds