I am new, three wekks into Ruby as my first Language. here is the code I already have:
=begin
this program is to calculate doubling a penny a day for thirty one days
=end
puts "how many days would you like to calculate"
days = gets.chomp.to_i
i = 1
loop do
puts "#{i}"
break i >=100
end
I have tried to use ** as this is they syntax for exponential use. I have considered an until loop also, but the thing I am having most difficulty with is how to double per day each integer for given time.
I have also tried "#{i**2}" , "#{i**i}" , I have tried to google this problem for the past 2 days, to no avail.
It can be done using a simple bit shifting operation. Binary value "1" shifted left n times is used to calculate 2^n.
puts "how many days would you like to calculate"
days = gets.chomp.to_i
puts 1 << (days - 1)
You don't need any loop here. What about a power? If you want to double 1 penny in 31 days, you need to calculate 2^30:
puts "how many days would you like to calculate"
days = gets.chomp.to_i
puts 2 ** (days - 1)
Try:
# Display the question to the user in the terminal
puts 'How many days would you like to calculate?'
# Get the number of days from stdin
days = gets.chomp.to_i
# starting at 1 and up to the number of days start doubling. Reduce returns the result back to itself, thus doubling the return of each number until you have reached the up to limit.
result = 1.upto(days).reduce { |start| start * 2 }
# Put the result
puts result
31.times.reduce 1 do |a| a * 2 end
#=> 2147483648
Related
I am currently working on a lab to create a countdown timer using a while loop and the subtract/assign operator. So far I have the loop counting 10 and breaking to 0 and printing my string "Happy New Year". I am not sure why it isn't iterating from 10 down to 0. Link to lab and code below https://learn.co/tracks/online-software-engineering-structured/procedural-ruby/looping/countdown-to-midnight-lab
number = 10
while number > 0
puts "#{number} SECOND(S)!"
number -= 1
break if n <= 0
puts "HAPPY NEW YEAR!"
end
end
There is one end too much. Proper indentation could have told you that.
puts "HAPPY NEW YEAR!" should probably be the last line, out of the loop (and probably without the puts).
n should be number
The task is in the form of a method which returns a string . puts however returns nil.
I wrote this program to ask users for their age, and then tell them how old they will be in 10-50 years. I don't understand what's wrong with it :( I'm just a beginner and any help would be greatly appreciated.
print "How old are you?"
age = gets.chomp
i = 1
while i < 6
multiple = i * 10 + age
puts "In #{multiple} years you will be #{multiple}"
i++
end
Many ways to accomplish what you're trying to do. Make sure you're indenting blocks correctly - it'll make your code much more readable. Note that to_i converts your input from a String to an Integer. Also, try to name your variables more specifically; multiple doesn't really mean anything in your example.
puts "How old are you?"
age = gets.chomp.to_i
(1..5).each do |i|
years_passed = i * 10
new_age = years_passed + age
puts "In #{years_passed} years you will be #{new_age}"
end
If you want to use a while loop, you could do:
puts "How old are you?"
age = gets.chomp.to_i
multiplier = 1
while multiplier <= 5
years_passed = multiplier * 10
new_age = years_passed + age
puts "In #{years_passed} years you will be #{new_age}"
multiplier += 1
end
I'm new to ruby and new to stack. I am trying to use the .each method on an array of numbers to see which numbers are divisible by 4, and 400. It is based on an exercises from Chris Pine's "Learn to Program" Ruby tutorial. In it you are supposed to find the leap years, then print them, from a range of years that the user inputs. I accomplished this using an if/else statement...but it seems to me this should be able to be done using the each method, or maybe the map method? Less code.
For example:
puts "Enter two years (to - from) to find out which years are leap years!"
puts "Enter the first year.."
year1 = gets.chomp.to_i
puts "Now enter the second year"
year2 = gets.chomp.to_i
range = (year1..year2).to_a
puts "These are the leap years between those years:"
range.each do |year|
leaps = (year % 4 == 0 || year % 400 == 0)
end
puts leaps
this code may not be correct, but i have toyed with different ways of doing it (puts inside .each, defining variable outside, etc...) but nothing seems to work. Like I said, I accomplished it with an if/else...I just feel there may be a better way, and it's driving me nuts. Do i not understand the .each correctly? am i using the wrong method? can it be done at all using each/map/or collect???? Thanks in advance!
You need to puts inside the each block too. Also, you can just divide by 4 and check if the remainder is 0. No need of 400
range.each do |year|
puts year if year % 4 == 0;
end
The puts year will be executed only if the if condition is satisfied.
def percent_more
puts "What is the biggest number?"
biggest_number = gets.chomp
puts "What is the smallest number?"
smallest_number = gets.chomp
difference = biggest_number.to_i - smallest_number.to_i
total_percent_more = difference / smallest_number.to_f
puts "Your biggest number is #{total_percent_more}% bigger then your smallest number. Don't forget to round off to the nearest whole percent!"
end
Now that code will tell you what percent more biggest_number is than smallest_number. But the problem is it prints out a long list of decimals, which are a pain to sort through. So if I wanted the code to only show say the first 3 numbers what would I do??
What you want to use is total_percent_more.round like so:
puts "What is the biggest number?"
biggest_number = gets.chomp
puts "What is the smallest number?"
smallest_number = gets.chomp
difference = biggest_number.to_i - smallest_number.to_i
total_percent_more = difference / smallest_number.to_f
puts "Your biggest number is #{total_percent_more.round}% bigger then your smallest number. Don't forget to round off to the nearest whole percent!"
See the docs for more info :
http://www.ruby-doc.org/core-2.1.2/Float.html#method-i-round
in ruby versions earlier than 1.9 you'll need to use sprintf like so:
puts "Your biggest number is #{sprintf('%.2f', total_percent_more)}% bigger then your smallest number. Don't forget to round off to the nearest whole percent!"
You can change the amount of decimal places by changing the number.
See docs for more details:
http://www.ruby-doc.org/core-1.8.7/Kernel.html#method-i-sprintf
result = 10/6.0
puts result
printf("%.3f\n", result)
--output:--
1.66666666666667
1.667
Here is an example how to round to 2 decimal places
amount = 342
puts amount.round(2)
If you wanted to round to the nearest 3 decimal places then something like:
puts amount.round(3)
CONSTANT = 1000000000000000000
array = (1..CONSTANT).to_a
start = Time.now
array.each do |i|
if 1000 < i < CONSTANT * 9 / 10
elsif i > CONSTANT * 9 / 10
else
end
end
finish = Time.now
puts "Running time: #{finish - start} seconds"
I wrote the above script in an attempt to figure out how much time saving could be achieved by re-ordering the control branches. The script froze my machine immediately after being run, which couldn't be terminated via CTL + C.
Could someone please point out what happened there?
You're iterating over a huge number.
Lets say your CPU can iterate one array item per nanosecond (which is good!), that means it'll take 1e9 seconds to iterate over the array. That's 31 years!
Your constant is far, far too large.
You are creating a huge array which you don't even need. That is forcing your machine to start paging (it would take up 5% of the 64-bit address space and your machine certainly doesn't have that much RAM). Your code is not making it to the loop (the condition in the if statement isn't valid ruby).
CONSTANT = 1000
# start with something small, then increase by 10
# 10000000 works for me.
start = Time.now
CONSTANT.times do |i|
if 1000 < i && CONSTANT * 9 / 10
elsif i > CONSTANT * 9 / 10
else
end
end
finish = Time.now
puts "Running time: #{finish - start} seconds"
What happened is that you tried to create a rather large array:
CONSTANT = 1000000000000000000
array = (1..CONSTANT).to_a
And your machine got upset with you. You might have better luck using the Range on its own without the to_a call.