CODEWITHSUNDEEP
ruby
SoSimple
SoSimple

Reputation: 701

converting binary to decimal - results too large

I'm trying to implement my own method of converting binary to decimal and I'm following the following example of calculating the decimal value of the binary string 101:

101 => 1*2^2 + 0*2^1 + 1*2^0 => 1*4 + 0*2 + 1*1 => 4 + 1 => 5

My method is

def to_decimal binary
  num_array = binary.to_s.split('').map(&:to_i)

  puts num_array.inject { |dec, num| dec + num * 2**(num_array.length-1) }
end

This seems to work fine for 1001 which gives 9 but 100 gives 1 and 11010 gives 33 when it should be giving 26. I've tried to look this up but I've found a few different ways to going about this and they're just confusing me even further.

Upvotes: 1

Views: 88

Answers (1)

EugZol
EugZol

Reputation: 6545

Instead of this:

num_array.inject{ |dec, num| dec + num * 2**(num_array.length-1) }

You meant this (multiplying by current power, and building decimal from the lowest to the highest power):

 num_array.reverse!
 num_array.each_index.inject(0){ |dec, index| dec + num_array[index] * 2**index }

Upvotes: 2

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