I am trying to convert a bit array, such as [0,0,1,0].to_i = 2 or [0,1,0,1].to_i = 5.
What possible ways are there to do this in Ruby?
2 Answers
Here's one way:
[1] pry(main)> [0,0,1,0].join.to_i(2)
=> 2
[2] pry(main)> [0,1,0,1].join.to_i(2)
=> 5
[3] pry(main)>
Comments
Here's a slightly more sophisticated snippet (as compared to Ryan's).
a1 = [0,0,1,0]
a2 = [0,1,0,1]
def convert a
a.reverse.each.with_index.reduce(0) do |memo, (val, idx)|
memo |= val << idx
end
end
convert a1 # => 2
convert a2 # => 5
4 Comments
Cadoiz
Question: does the usage of
.reverse instead of .reverse! make a difference? If I understood correctly, the first one should consume double the memory, right
Sergio Tulentsev
@Cadoiz
reverse! mutates the original array. This has many consequences. One of which is if you convert the same array twice, you'll get different results. convert(a1); convert(a1)Sergio Tulentsev
@Cadoiz: but! instead of
reverse.each, we can use reverse_each which does not build a temp array and does not touch the original array.Cadoiz
Especially the latter is great knowledge for me. It's unfortunately not there for my ancient linux, but it definitely is for ruby >2.6.10. I don't know how to find out earlier compatibility.
input.to_s(2).each_char.map { |c| c == '1' }isn't cutting it for huge numbers.