There is a song that goes like this: On the first day of Christmas, my true love sent to me a partridge in a pear tree. On the second day of Christmas, my true love sent to me two turtle doves and a partridge in a pear tree. ... If this goes on for the 12 days of Christmas. How many presents will your true love send you over Christmas? <strong>(Hint: You will need a loop inside another). </strong> I don't think you need a loop inside a loop.... Here is what I did: day = 0 gifts = 0 12.times do day = day + 1 gifts = gifts + day end print gifts Does anyone know how you would do it with a <em>loop inside a loop</ em>?

on 2007-06-18 18:51

on 2007-06-18 19:10

I'm not sure why you'd want to, but I suppose you could do something like: gifts=0 (1..12).each do |i| (1..i).each { |j| gifts += 1 } end puts gifts

on 2007-06-18 19:20

Wouldn't it be this... gifts = 0 (1..12).each do |x| (1..x).each do { |y| gifts += y } end puts gifts Note the difference between mine and yours, where I count each item instead of each set. So 5 gold rings counts as 5 instead of 1. I think it all depends on how the original question was intended.

on 2007-06-18 19:21

I just wanted to do the challenge correctly... Although, maybe I shouldn't be doing a tutorial with that kind of lame challenge...

on 2007-06-18 19:29

On 6/18/07, danielj <danielj@sleepingindian.org> wrote: > your true love send you over Christmas? > end > > print gifts > > Does anyone know how you would do it with a <em>loop inside a loop</ > em>? Note that your program does not solve the problem (which is easy to misinterpret). To clarify the problem: On day 1, you get 1 gift. On day 2, you get 3 gifts, not two (two doves AND one bird/tree combo). On day 3, you get 6 gifts - 3 hens, 2 doves, one more pear tree w/attendant partridge. and so on... until On day 11 you get 66 gifts, and On day 12 you get 78 gifts. Do you see how a loop within a loop may be helpful? Good luck! -A

on 2007-06-18 19:32

Remember to count each gift for each day (on the second day you get another bird in a tree, on the third day you get two more doves and another bird in a tree, etc.) day = 0 gifts_for_the_day = 0 total_gifts = 0 12.times do day += 1 gifts_for_the_day += day total_gifts += gifts_for_the_day puts "Day: #{day}, Gifts for Day: #{gifts_for_the_day}, Total gifts: #{total_gifts}" end -- Stephen

on 2007-06-18 19:45

Alex LeDonne schrieb: >> If this goes on for the 12 days of Christmas. How many presents will >> gifts = gifts + day > > > Good luck! > > -A > Well, I solved this for fun, my code looks like this: def gift_counter(max = 12) gifts = 0 1.upto(max) do |day| gifts += day # I guess 'day' is a bad var-name here :D puts "Day: {#day}, Gifts: #{gifts}" end end It works quite good, so why does this Quiz-Site suggest to use two loops? Am I getting something of this quiz wrong?

on 2007-06-18 19:51

On 6/18/07, Daniel Kempkens <Daniel.Kempkens@gmail.com> wrote: > >> > >> day = day + 1 > > misinterpret). To clarify the problem: > > Do you see how a loop within a loop may be helpful? > gifts += day # I guess 'day' is a bad var-name here :D > puts "Day: {#day}, Gifts: #{gifts}" > end > end > > It works quite good, so why does this Quiz-Site suggest to use two > loops? Am I getting something of this quiz wrong? > Well, the original question is: What is the total number of gifts given over the 12 days? The gift_counter is good for the number by-the-day, but the question is asking for a gift_totaler. -A

on 2007-06-18 19:55

On Jun 18, 11:42 am, Daniel Kempkens <Daniel.Kempk...@gmail.com> wrote: > Alex LeDonne schrieb: > > On day 1, you get 1 gift. > > On day 2, you get 3 gifts, not two (two doves AND one bird/tree combo). > > On day 3, you get 6 gifts - 3 hens, 2 doves, one more pear tree > > w/attendant partridge. > It works quite good, so why does this Quiz-Site suggest to use two > loops? Am I getting something of this quiz wrong? Does it work? It tells you how many gifts you GET on each day, but does not tell you how many gifts you HAVE when the day is done. On day 1 you get 1 gift, resulting in 1 gift owned by you. On day 2 you get 3 gifts, resulting in 4 gifts owned by you. On day 3 you get 6 gifts, resulting in 10 gifts owned by you.

on 2007-06-18 20:11

I originally thought it boiled down to 1+2+...+11+12=78 But now that I think about it again, I'm pretty sure I was wrong. The correct sequence is: (1) + (1+2) + (1+2+3) + ... + (1+2+...+11+12) Which I think makes you right. Sam

on 2007-06-18 20:35

Phrogz schrieb: >> def gift_counter(max = 12) > Does it work? It tells you how many gifts you GET on each day, but > does not tell you how many gifts you HAVE when the day is done. > > On day 1 you get 1 gift, resulting in 1 gift owned by you. > On day 2 you get 3 gifts, resulting in 4 gifts owned by you. > On day 3 you get 6 gifts, resulting in 10 gifts owned by you. > I think I missed the total-part of the quiz ;) But implementing a total-counter wouldn't be much difficult.

on 2007-06-18 21:06

I see... Thanks all... It was really helpful to see the problem thought about many different ways

on 2007-06-18 21:42

On 6/18/07, Daniel Kempkens <Daniel.Kempkens@gmail.com> wrote: > I think I missed the total-part of the quiz ;) But implementing a > total-counter wouldn't be much difficult. Wouldn't it be: def fact(n); n > 1 ? n + fact(n-1) : 1; end puts (1..12).inject(0) { |s,r| s + fact(r) }

on 2007-06-18 21:56

On Jun 18, 3:40 pm, "Gregory Brown" <gregory.t.br...@gmail.com> wrote: > Wouldn't it be: > > def fact(n); n > 1 ? n + fact(n-1) : 1; end > puts (1..12).inject(0) { |s,r| s + fact(r) } That certainly works, although I'm personally uncomfortable with the name of your recursive method; "fact" seems to imply factorial, which this is not. If you like inject, how about a pair of 'em: puts (1..12).inject(0) { |sum, day| sum + (1..day).inject { |day_sum, gifts| day_sum + gifts } } Eric ---- Are you interested in on-site Ruby training that uses well-designed, real-world, hands-on exercises? http://LearnRuby.com

on 2007-06-18 23:04

On Jun 18, 2007, at 1:19 PM, Matt Filizzi wrote: > Wouldn't it be this... > > gifts = 0 > (1..12).each do |x| > (1..x).each do { |y| gifts += y } ^^ > end > puts gifts Not quite. It should be: <code> gifts = 0 (1..12).each do |x| (1..x).each { |y| gifts += y } end gifts # => 364 </code> But this problem has a nice closed-form solution: <code> def gifts(days) days * (days +1) * (days + 2) / 6 end gifts(12) # => 364 </code> Regards, Morton

on 2007-06-18 23:10

On 6/18/07, Eric I. <rubytraining@gmail.com> wrote: > On Jun 18, 3:40 pm, "Gregory Brown" <gregory.t.br...@gmail.com> wrote: > > Wouldn't it be: > > > > def fact(n); n > 1 ? n + fact(n-1) : 1; end > > puts (1..12).inject(0) { |s,r| s + fact(r) } > > That certainly works, although I'm personally uncomfortable with the > name of your recursive method; "fact" seems to imply factorial, which > this is not. Dur. You're right. 12! = 12*11*10*.. /me is a math major, too. > If you like inject, how about a pair of 'em: > > puts (1..12).inject(0) { |sum, day| > sum + (1..day).inject { |day_sum, gifts| day_sum + gifts } > } yup, that looks pretty good.

on 2007-06-18 23:17

Eric I. wrote: > puts (1..12).inject(0) { |sum, day| > sum + (1..day).inject { |day_sum, gifts| day_sum + gifts } > } I'd do it as shown below, but it's probably not covered by the point in the book you're currently at: irb(main):001:0> class Integer irb(main):002:1> def int_sum irb(main):003:2> (1..self).inject(0){|sum,n|sum+n} irb(main):004:2> end irb(main):005:1> end => nil irb(main):006:0> puts (1..12).inject(0){|sum,n|sum+n.int_sum} 364 => nil