Oddball_sum Help Request

Rails
1

Hi,

I am new to Ruby on Rails. I am practicing problems to better
understand coding. I understand the logic but I am not able to put in
proper codes. Could someone please solve the following problem for me?

oddball_sum
Write a function oddball_sum(numbers), which takes in an array of
integers and returns the sum of all the odd elements.

oddball_sum(numbers)
i = 0
while i < numbers.length
if (numbers % 2 !== 0)
return numbers[i] += 1
i += 1
end
return result
end

2

On 4 August 2015 at 03:56, Dhaval B. [email protected] wrote:

oddball_sum(numbers)
You need a def on the front of the above

i = 0

You need a variable to hold the sum, so
result = 0

while i < numbers.length
if (numbers % 2 !== 0)

you meant numbers[i] % 2 != 0

return numbers[i] += 1

Don’t return here, add this number to the total
result += numbers[i]

i += 1
end
return result
end

But in fact it is better to use each, not a while loop, so something
like

def oddball_sum(numbers)
result = 0
numbers.each { |n| result += n if n %2 != 0 }
return result
end

In fact there are even more concise ways of coding this, but I would
stick with something like the above for the moment in order to keep
the code readable.
I suggest you find some tutorials on Ruby first and work through them,
then when you think you have the basics of Ruby sorted move on to a
good Rails tutorial such as railstutorial.org, which will show you the
basics of Rails.

Colin

3

When I looked at your code sample, I immediately thought that I should
look
at the *Ruby *Integer, Emumerable and Array API. I reviewed them…
On review of the Ruby Integer API revealed the method .odd?
On review of the Ruby Array API revealed the methods .select
On review of the Ruby Enumerable API revealed the methods .reduce

So I built the solution, but from what I learned that are many
possibilities, and admittedly this solutions may not be the best or the
fastest

my_odd_ball_sum = numbers.select {|n| n.odd?}.reduce(:+)

Breakdown…

numbers.select
select { |item| block } → new_ary
select → Enumerator

Returns a new array containing all elements of ary for which the given
block
returns a true value.

numbers.select {|n| n.odd?} returns an Enumerator, so then apply
reduce(:+)
reduce(sym) → obj

Combines all elements of enum by applying a binary operation,
specified
by a block or a symbol that names a method or operator.

My point is that it is a good idea/investment to explore *Ruby *API for
solutions.
Hope this helps
Liz

4

Thank you Liz :slight_smile:

5

Colin,

That’s very helpful.

Sorry, I copy-pasted the codes I had from my word file so I missed the
“def.”

Anyway,

Thank you for explaining. I have two more questions which I will ask in
another thread after I finish doing them on my own.

Do you have a personal e-mail I can reach you on? I would love to pick
your brain if you give me a chance.

Best,

DB

Colin L. wrote in post #1177221:

On 4 August 2015 at 03:56, Dhaval B. [email protected] wrote:

oddball_sum(numbers)
You need a def on the front of the above

i = 0

You need a variable to hold the sum, so
result = 0

while i < numbers.length
if (numbers % 2 !== 0)

you meant numbers[i] % 2 != 0

return numbers[i] += 1

Don’t return here, add this number to the total
result += numbers[i]

i += 1
end
return result
end

But in fact it is better to use each, not a while loop, so something
like

def oddball_sum(numbers)
result = 0
numbers.each { |n| result += n if n %2 != 0 }
return result
end

In fact there are even more concise ways of coding this, but I would
stick with something like the above for the moment in order to keep
the code readable.
I suggest you find some tutorials on Ruby first and work through them,
then when you think you have the basics of Ruby sorted move on to a
good Rails tutorial such as railstutorial.org, which will show you the
basics of Rails.

Colin

6

You win all the points. That is slick!

Walter