convert_binary_to_decimal_and_decimal_to_binary.rb

# 1. Make a ruby method that takes a number in base 2 (binary, as a string) and converts it to a decimal (not using the inbuilt ruby methods).

def binary_to_decimal(binary)
    binary = binary.split("").map(&:to_i)
    # this splits binary numbers into an array and turns them into integers 
    exp = binary.length - 1
    # => 5
    # this determines the starting point of the exponential, we have to minus 1 to get the correct exp, we need the last exp to be 2 ** 0
    base_array = []
    while exp >= 0
        # while 5 is greater than or equal to 0 do this, we need to do the 0 as we need the last base to be 1, when exp gets to -1 the while loop stops
        base = 2 ** exp
        # we start with 2 to the power of 5
        # => 32
        base_array << base 
        exp -= 1
    end
    # this gets me a base_array, each item in this array correlates with each item in the binary array 
    # => [32, 16, 8, 4, 2, 1]
    index = 0
    exp = binary.length
    # we reset the exp, we don't need to add anything this time
    results = []
    while index < exp 
        if binary[index] == 1
            # if the binary index is equal to one that means it takes the to the power of value
            results << base_array[index]
        end 
        index += 1
    end 
    # sum the array with the base_array values in it
    return results.sum
end 
p binary_to_decimal("001100")

# 2. Make a ruby method that takes a number in decimal (base 10, as an integer), and converts it to base 2 (binary - which will have to be a string).

def decimal_to_binary(decimal)
    decimal = decimal.to_i 
    # we need to turn decimal to an integer so we can do math on it
    binary = []
    while decimal > 0
        result = decimal % 2
        # this returns either 1 or 0 remainders for each decimal, the decimal is changed in each while cycle below
        binary << result
        decimal = (decimal / 2.0).floor
        # this math concept comes from this https://www.wikihow.com/Convert-from-Decimal-to-Binary example where you continue to divide by 2 until you reach 0
    end  
    # the array comes back in the reverse order so we just do a simple .reverse to make it perfect
    return binary.reverse.join
end 
p decimal_to_binary("10002223")