sop.rb

class Canonical
    def initialize(eq)
        @eq = eq.split('+')
        @new_eq = []
    end
    

    def binary_to_decimal(x)
        y = 1
        z = 0
        x.gsub(/ /,'').reverse.scan(/(0|1)/).each do |x|
            z = z + (y * x[0].to_i)
            y *= 2
        end
        z
    end
    
    def missing?
       @missing = []
       index = 0
       for e in @eq
          if e.index('a').nil?
              @missing << 'a'
          end
          if e.index('b').nil?
              @missing << 'b'
          end
          if e.index('c').nil?
              @missing << 'c' 
          end
          if e.index('a') && e.index('b') && e.index('c')
              @missing << ''
          end
          #p "Term " + index.to_s + " missing: " + @missing[-1] if @missing[-1] != ''
          index+=1
       end
        
       
    end
    
    def show
        @ordered_hash = {}
        bin = {}
        #p "SHOWING"
        tmp = ''
        index = 0
        for e in @new_eq
            bin[binary_to_decimal(e.gsub("a'", "0").gsub("b'", "0").gsub("c'", "0").gsub("a", "1").gsub("b", "1").gsub("c", "1"))] = e  
            index+=1
        end
        show = []
        bin.sort.collect{|k,v| show << v } 
        p show.join('+')
    end
    
    def insert_missing
       index = 0
       for e in @eq
           #p "Working on: " + e
           if @missing[index].size > 0
               @new_eq << e+@missing[index]
               @new_eq << e+@missing[index]+"'"
            else 
                @new_eq << e
            end 
           index += 1
       end 
    end
    
    def show_eq
       p @eq.join('+')
    end
end

q = Canonical.new("a'b'c+a'b'c'+abc'+a'bc'+abc+abc'+ab'c+ab'c'")
q.show_eq
q.missing?
q.insert_missing
p " ----> "
q.show