Triangle numbers are the sums of successive integers. So 6 is a triangle number because
6 = 1 + 2 + 3
which can be displayed in a triangular shape like so
*
* *
* * * Thus 6 = triangle(3). Given n, return t, the triangular number for n.
Example:
Input n = 4 Output t is 10
Solution Stats
Problem Comments
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16 Comments
Show
13 older comments
Vipresh Gangwal
on 18 Jan 2013
i dint realize i was writing a code for sum of first n natural numbers instead of computing n*(n+1)/2
Chris McComb
on 12 Jul 2013
Man, this takes me back to algebra... Its more fun in MATLAB tho!
RICHARDSON
on 3 Nov 2013
It's interesting to work with and building the confidence to solve problems....nice
Jeevan Thomas
on 12 Nov 2013
Good one. Reminds me of those old school days..!!
Jon
on 13 Nov 2013
All solutions with score 10 or 11 use the regexp cheat.
Dai
on 12 Apr 2014
Jon or anybody!
Can you explain how the regexp cheat works?
Nick H
on 15 Jul 2014
How do you reduce the size of your code?
Henry Cervantes
on 17 Feb 2015
mucha fantasía en el titulo
Mei Lamb
on 4 Jun 2015
what it means?
Mei Tian
on 23 Dec 2015
I really had to use my brain for this problem
Noriko Hounoki
on 8 Dec 2016
Interesting!
Eqin Azlan
on 29 Dec 2016
sound simple but annoying
Loris Chavée
on 16 Jul 2017
Funny and interesting problem!
BOZHI CHEN
on 14 Aug 2017
good!
Shounak Shastri
on 23 Feb 2018
For clarity sake,
t = triangle (n)
We need to calculate t for a given n
Rupesh Gosavi
on 6 Feb 2019 at 9:23
It is pretty easy but tricky!
Solution Comments
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3 Comments
Samidha Banka
on 19 Jan 2018
Simple, yet nice.
Luyu Wang
on 8 Jul 2018
I solved it bot by the best algorithm.
Ashish Patil
on 2 Aug 2018
I also used this one. but while using other methods(not optimized), when i tried commands mentioned below, it gave "failed" status.
Can anybody tell why?
function t = triangle(n)
y= x:-1:1;
y= sum(y)
end
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1 Comment
David Tandri
on 4 Aug 2017
mantap jaya!!!
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1 Comment
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
very easy
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2 Comments
Devan Rao
on 10 Jan 2017
good
ubaid haroon
on 3 Mar 2017
would you like a cookie?
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1 Comment
sim yoke meng
on 20 Dec 2016
:P
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1 Comment
Mike Murray
on 4 Nov 2016
test
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1 Comment
Steven He
on 1 Aug 2016
Just the sum of 1 to n
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2 Comments
Harish Babu Kankanala
on 30 Jun 2016
How can the above solution be improved?
Jan Orwat
on 2 Jul 2016
You can use Gauss formula for triangular numbers. It will improve performance. It won't improve Cody size. To improve Cody size, you need hack. Popular hack is to wrap the code into regular expression. Somebody invented it to cheat scoring algorithm and it spreaded among cody submissions like a cancer. I'm not proud of this, I was using this hack too, fortunately realised that it makes no sense. Advice: don't care so much about the size, care about quality code. Most of super small solutions use some sort of cheats, you won't learn much from those.
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2 Comments
bacetiner
on 12 May 2016
I believe you can have a more efficient solution if you get rid of the intermediate variable A.
ubaid haroon
on 3 Mar 2017
fancy pants
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2 Comments
Pankaj Soni
on 23 Apr 2016
% correct solution
function triangle(n)
t=n;
clc
if n >1
for l = 1:1:(t-1)
l = l+1;
end
for i=1:1:l
for k = l:-1:i
fprintf(' ');
end
for j = 1:1:i
fprintf('* ');
end
fprintf('\n');
end
else
fprintf(' *\n');
end
Pankaj Soni
on 23 Apr 2016
%please check why this is not compiling
function prac(n)
t=n;
clc
if n >1
for l = 1:1:(t-1)
l = l+1;
end
for i=1:1:l
for k = l:-1:i
fprintf(' ');
end
for j = 1:1:i
fprintf('* ');
end
fprintf('\n');
end
else
fprintf(' *\n');
end
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1 Comment
Kingfall
on 2 Apr 2016
Not sure why it failed to evaluate? Not allow to use built-in functions?
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1 Comment
Dennie
on 31 Mar 2016
i guess there is always a better solution to everything
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1 Comment
Ravi
on 29 Mar 2016
>> sum(1:5)
ans =
15
>> sum(1:6)
ans =
21
>> sum(1:3)
ans =
6
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1 Comment
sarah haras
on 16 Feb 2016
:)
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1 Comment
Soumyadip Das
on 12 Jan 2016
Good one
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1 Comment
Lily Waddell
on 23 Dec 2015
niec job mie u did rly weel
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1 Comment
Dale Crawford
on 7 Dec 2015
I think this works for very low numbers but as you get higher, a work around that might be faster is
n*(n+1)/2
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1 Comment
MD. Muhtady Muhaisin
on 1 Jul 2015
can anyone suggest how to improve the size of the code?
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1 Comment
Christopher Creutzig
on 24 Jul 2014
Too bad the computationally inferior solution is better in terms of points.
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1 Comment
Vishal
on 23 Apr 2014
good
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1 Comment
Céline
on 11 Apr 2014
Well done!
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1 Comment
Raja
on 5 Feb 2014
simple and nice!
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1 Comment
Matt
on 30 Jan 2014
Compared this solution score to sum(1:n). Using tic toc and varying sizes of n repeated up to 1,000,000 times I found that n*(n+1)/2 is by far faster. On the order of 10,000 times faster.
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1 Comment
Ammar
on 30 Dec 2013
Have no idea how I can have a size of 10!!
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1 Comment
Anand
on 18 Dec 2013
How to calculate the solution size ?
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2 Comments
Micah Beckman
on 5 Sep 2016
Okay, so we can definitely do better than a for loop...
Zhengyi
on 21 Mar 2018
@Micah Beckman no, this solution is not an "efficient" answer even though it scores high... one should use sum(1:n) to replace a for loop sum.
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1 Comment
John D'Errico
on 28 Jan 2012
Of course, this solution, while short, is NOT the best solution! Clearly the best solution is the far more efficient: n*(n+1)/2
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