puts "enter a number"
x = gets.chomp.to_i
y = 0
while x != 1
y += 1
if x % 2 == 0
x = x / 2
else
x = x*3 + 1
end
print "#{x} "
end
puts "\nThe number of sequence is #{y+1}"
Hi, if I key in negative number or 0, I will get an infinite loop. How do I avoid entering the loop if my number is 0 or negative.
You can use x > 1 i.e
puts "enter a number"
x = gets.chomp.to_i
# if you want to consider negative as positive then x = gets.chomp.to_i.abs
y = 0
while (x > 1)
y += 1
if x % 2 == 0
x = x / 2
else
x = x*3 + 1
end
print "#{x} "
end
puts "\nThe number of sequence is #{y+1}"
Hope it helps
To answer your question:
Your code works perfectly well and does exactly what it is told to do:
while x is not 1 OR x is smaller than 0 do this codeblock.
If you set x to a negative number, x will never be a positive number, so it runs forever (because x is always smaller 0).
So, the code is correct, but there is a flaw in the logic behind it :)
Related
puts "Enter range(starts at 1), ends at the number that you enter: "
range = gets.chomp.to_i
number = 1
while number <= range
temporary_number = number
sum_angstrom = 0
number += number
while(temporary_number != 0)
digit = temporary_number % 10
temporary_number /= 10
sum_angstrom = sum_angstrom + (digit ** 3)
end
if (sum_angstrom == number)
puts number
end
end
This time, I tried to make a program to show the armstrong numbers in a range that's taken from the user's input. The program just stops after I enter the number and press enter and i can't figure out why.
Keep in mind that i can't use for(each), that's why i'm using while so often.
First of all, change number += number to number += 1; otherwise you will only test the powers of 2.
Second, move the number += 1 line at the bottom of the while block it is in. Otherwise you will always test if sum_armstrong(n) == n+1.
This works:
puts "Enter range(starts at 1), ends at the number that you enter: "
range = gets.chomp.to_i
number = 1
while number <= range
temporary_number = number
sum_angstrom = 0
while(temporary_number != 0)
digit = temporary_number % 10
temporary_number /= 10
sum_angstrom = sum_angstrom + (digit ** 3)
end
if (sum_angstrom == number)
puts number
end
number += 1
end
Armstrong Number in Ruby one liner
n = 153
s = 0
n.to_s.split("").map{|e| s+=(e.to_i*e.to_i*e.to_i)}
puts (n==s ? "Armstrong number" : "Not Armstrong number")
You can iterate in a range to print the value based on your requirement.
Main logic lies in below line.
n.to_s.split("").map{|e| s+=(e.to_i*e.to_i*e.to_i)}
Improving my answer a little bit
n.digits.map{|e| s+=(e**3)}
I wrote code to find how many operations a number required under the Collatz Conjecture. However, my operations variable doesn't seem to be incrementing.
My code is:
puts "Please input a number"
number = gets.chomp
number = number.to_i
operations = 0
modulo = number % 2
while number =! 1
if modulo == 0
number = number / 2
operations = operations + 1
elsif modulo =! 0 && number =! 1
number = number * 3
number = number += 1
operations = operations + 2
else
puts "Uh oh, something went wrong."
end
end
puts "It took #{operations} operations!"
I am running this code on https://www.repl.it.
First of all, it's elsif; not elseif (I edited that in your question). And unequal sign is !=; not =!. But that has a somewhat different meaning. (i.e.: number =! 1 means number = !1)
In the 12th line, what is number = number += 1? I think you meant number += 1 or number = number + 1.
Now, the code works. :)
Here's the final version.
puts "Please input a number"
number = gets.chomp
number = number.to_i
operations = 0
modulo = number % 2
while number != 1
if modulo == 0
number = number / 2
operations = operations + 1
elsif modulo != 0 && number != 1
number = number * 3
number = number + 1
operations = operations + 2
else
puts "Uh oh, something went wrong."
end
end
puts "It took #{operations} operations!"
Usage:
Please input a number
256
It took 8 operations!
An optimal solution using functions:
def collatz(n)
if n % 2 == 0
return n / 2
else
return 3*n + 1
end
end
def chainLength(num)
count = 1
while num > 1
count += 1
num = collatz(num)
end
return count
end
puts "Please input a number"
number = gets.chomp
number = number.to_i
operations = chainLength(number)
puts "It took #{operations} operations!"
If you need more performance, read about dynamic programming and memoization techniques.
I'm trying to make a simple * pyramid using while loops but it stops at the first five *. I can't figure out why.
This is my code:
x = 5
y = 0
while x > 0
while y < x
print "*"
y +=1
end
x -= 1
end
You never reset y or print a new line
x = 5
y = 0
while x > 0
while y < x
print "*"
y +=1
end
print "\n"
y = 0
x -= 1
end
Output
*****
****
***
**
*
That is bad Ruby tho
This is a much more idiomatic solution
5.downto(1) do |x|
1.upto(x) do |y|
print "*"
end
print "\n"
end
Output
*****
****
***
**
*
I don't know what the final shape of "pyramid" you're looking for, but you can likely adapt the technique above to get the desired output
Factorial 1 and 2 works but 3 and 4 do not. I've worked the steps out on paper and do not see why they do not work. Any help is much appreciated.
def factorial(n)
x = 1
y = n
while x < n
n = n * (y-x)
x = x + 1
end
return n
end
puts("factorial(1) == 1: #{factorial(1) == 1}")
puts("factorial(2) == 2: #{factorial(2) == 2}")
puts("factorial(3) == 6: #{factorial(3) == 6}")
puts("factorial(4) == 24: #{factorial(4) == 24}")
The reason it's not working is that after each loop the value of n gets bigger and the condition x < n keeps executing until it hits a point where n becomes zero. If you pass 3 to the function on the third loop you will have:
while x(3) < n(6)
n(6) = n(6) * (y(3) - x(3))
end
therefore n becomes 0 causing the loop to exit on the next round and the return value is obviously 0. To fix it you just need to replace n with y in the while condition:
while x < y
As a side note just another interesting way you could solve the factorial problem using recursion is:
def factorial(n)
n <= 1 ? 1 : n * factorial(n - 1)
end
Try this:
def factorial(n)
if n < 0
return nil
end
x = 1
while n > 0
x = x * n
n -= 1
end
return x
end
I'm new to programming and I'm trying to program something but there's some kind of syntax error which I can't work out. Any help would be much appreciated. Here's my code:
begin
puts"Enter a number to count, or to exit type 0."
y = gets.chomp.to_i
if y == 0
exit
end
puts"Now put the number you're starting with"
x = gets.chomp.to_i
if y + x == 12 or y + x < 12
print x + y
end
if y + x > 12
n = y + x - 12
end
begin
if n < 12 or n == 12
print n
end
if n > 12
n = n - 12
end
end until if n < 12 or n == 12
end until y == 0
end
Your use of until if if wrong. They are each control sequences. You shouldn't need both.
Your n is not visible later in the code. Declare n=0 for example before if y + x > 12 to make it visible and accessible in the relevant code blocks.
Then, until if is wrong, this should simply be until
Lastly, delete the last end keyword.