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
Related
I'm very new in MATLAB (this is my first script).
I wonder how may I speed up this loop, I don't know any toolbox or 'tricks' as I'm a newbie on it. I tried to code it with instinct, it works, but it is really long.
All are variables get with fread or integer manually entered, so this is basically simple math, but I have no clue on why is it so long (maybe nested loops ?) and how to improve, as I am more familiar with Python and for example multiprocess.
Thanks a lot
X = 0;
Points = [0,0,0];
for i=1:nbLines
for j=1:nbPositions-1
if lDate(i)>posDate(j) && lDate(i)<=posDate(j+1)
weight = (lDate(i) - posDate(j)) / (posDate(j+1)- posDate(j));
X = posX(j)*(1-weight) + posX(j+1) * weight;
end
end
if X ~= 0
for j=1:nbScans
Y = - distance(i,j) / tan(angle(i,j));
Points = [Points;X, Y, distance(i,j)];
end
end
end
X = 0;
Points = cell([],1) ;
Points{1} = [0,0,0];
count = 1 ;
for i=1:nbLines
id = find(lDate(i)>posDate & lDate(i)<=posDate) ;
if length(id) > 1
weight = (lDate(i) - posDate(id(1))) / (posDate(id(end))- posDate(id(1)));
X = posX(id(1))*(1-weight) + posX(id(end)) * weight;
end
if X ~= 0
j=1:nbScans ;
count = count+1 ;
Y = - distance(i,j)./tan(angle(i,j));
Points{count} = [repelem(X,size(Y,2),size(Y),1), Y, distance(i,j)'];
end
end
You have one issue with the given code. The blow line:
Points = [Points; X, Y, distance(i,j)];
This will definitely slow up your code. You need to initialize this array to store the numbers. If you initialize it, you will find good difference in speed.
X = 0;
Points = zeros([],3) ;
Points(1,:) = [0,0,0];
count = 1 ;
for i=1:nbLines
for j=1:nbPositions-1
if lDate(i)>posDate(j) && lDate(i)<=posDate(j+1)
weight = (lDate(i) - posDate(j)) / (posDate(j+1)- posDate(j));
X = posX(j)*(1-weight) + posX(j+1) * weight;
end
end
if X ~= 0
for j=1:nbScans
count = count+1 ;
Y = - distance(i,j) / tan(angle(i,j));
Points(count,:) = [X, Y, distance(i,j)];
end
end
end
Note that, you code only saves the last value of X, is this what you want?
try using parallelization- "parfor" instead of "for" that uses all available processors.
parfor i=1:nbLines
rest of code here
end
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 :)
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.
s is a string, This seems very long-winded - how can i simplify this? :
if x === 2
z = s
elsif x === 3
z = s+s
elsif x === 4
z = s+s+s
elsif x === 5
z = s+s+s+s
elsif x === 6
z = s+s+s+s+s
Thanks
Something like this is the simplest and works (as seen on ideone.com):
puts 'Hello' * 3 # HelloHelloHello
s = 'Go'
x = 4
z = s * (x - 1)
puts z # GoGoGo
API links
ruby-doc.org - String: str * integer => new_str
Copy—Returns a new String containing integer copies of the receiver.
"Ho! " * 3 #=> "Ho! Ho! Ho! "
z=''
(x-1).times do
z+=s
end
Pseudo code (not ruby)
if 1 < int(x) < 7 then
z = (x-1)*s
For example for a rating system up to 5 stars you can use something like this:
def rating_to_star(rating)
'star' * rating.to_i + 'empty_star' * (5 - rating.to_i)
end