Question

I have array of 0’s and 1’s. And I need a function which return ‘next’ array. Something like this:

f([0,0,0,0]) -> [0,0,0,1]
f([0,0,0,1]) -> [0,0,1,0]
f([0,1,1,1]) -> [1,0,0,0]

Is there any library function or do I need to coding it myself ?

Answer 1

Ruby includes a simple way to convert between binary and base 10.

"0010".to_i(2)
=> 2

13.to_s(2)
=> "1101"

So a simple way to do what you need is

def f(a)
  (a.join.to_i(2) + 1).to_s(2).split("").map{ |v| v.to_i }
end

Here is a way to add two nbit numbers.

def nbit_addition(a, b)
  bit1 = toBits(a)
  bit2 = toBits(b)
  bitLength = bit1.length > bit2.length ? bit1.length : bit2.length
  bit3 = []
  for i in 0...bitLength
    bit1[i] = 0 if bit1[i].nil? 
    bit2[i] = 0 if bit2[i].nil? 
    bit3[i] = 0 if bit3[i].nil?
    bit3[i] += (bit1[i] + bit2[i])
    if bit3[i] > 1 
      bit3[i + 1] = 0 if bit3[i + 1].nil?
      bit3[i] %= 2
      bit3[i + 1] += 1
    end 
  end 
  bit3.join.to_s.reverse.to_i(2)
end 

def toBits(value)
  bit = []
  value.to_s(2).reverse.split(//).each { |b| bit << b.to_i } 
  return bit 
end