Independence Day weekend puzzler
11 views (last 30 days)
Show older comments
Inspired by an assignment in my son's Java programming class:
Write a one-liner that takes as input an array of numbers (e.g. x = [1 2 3]) and which outputs an array of integers that is "incremented" properly, (in this case, y = [1 2 4]).
Examples of proper input/output:
x = [1 9 1 9] ----> y = [1 9 2 0]
and
x = [9 9 9] ----> y = [1 0 0 0]
No semicolons allowed in your one line!
7 Comments
Paulo Silva
on 4 Jul 2011
+1 vote for the interesting puzzler, it's the first vote!
Please vote on it if you found it interesting and you want more of them.
Accepted Answer
Fangjun Jiang
on 3 Jul 2011
I like this Golf challenge. Inspired by Paulo's entry.
num2str(str2num(sprintf('%d',x))+1)-'0'
is shorter.
0 Comments
More Answers (8)
Jan
on 3 Jul 2011
My submission is neither a one-liner nor free of semicolons. But the total number of lines and semicolons is less than in STR2NUM and NUM2STR, which have 86 and 217 lines and call INT2STR in addtion.
n = length(x);
q = find(x ~= 9, 1, 'last');
if isempty(q) % [9, 9, 9, ...]
x = 1;
x(n + 1) = 0; % or x = [1, zeros(1, n)]
else % Any non-9 is found
x = [x(1:q - 1), x(q) + 1, zeros(1, n - q)];
end
1 Comment
Andrei Bobrov
on 3 Jul 2011
str2num(num2str(10.^(length(x)-1:-1:0)*x'+1)')'
ADD
z = 10.^(numel(x)-1:-1:0)*x'+1
y = round(rem(fix(z.*10.^-(fix(log10(z)):-1:0))*.1,1)*10)
2 Comments
David Young
on 3 Jul 2011
One-liner, avoiding string operations:
diff([0 (floor((sum(x.*10.^(length(x)-1:-1:0))+1) ./ 10.^(floor(log10(sum(x.*10.^(length(x)-1:-1:0))+1)):-1:0))) .* 10.^(floor(log10(sum(x.*10.^(length(x)-1:-1:0))+1)):-1:0)]) ./ 10.^(floor(log10(sum(x.*10.^(length(x)-1:-1:0))+1)):-1:0)
EDIT: This is only one line of code, even though formatting on the Answers web page makes it look like 4 lines.
3 Comments
Jan
on 4 Jul 2011
+1: A one-liner without calls to other M-files and therefore even no hidden semicolons.
Paulo Silva
on 3 Jul 2011
x=[1 2 3]; %example input
xr=num2str(str2num(strrep(num2str(x),' ',''))+1)-'0'
%xr =[1 2 3 4]
0 Comments
David Young
on 4 Jul 2011
Also one line of code (formatting for the web page will display it over more than one line of text):
double(regexprep(char(x), {['([' char(0:8) ']?)(' char(9) '*)$'] ['^(' char(0) '+)$']}, {'${char($1+1)}${regexprep($2,char(9),char(0))}' [char(1) '$1']}))
1 Comment
David Young
on 4 Jul 2011
This one works for long vectors with thousdands of elements (my arithmetic-based solution doesn't).
David Young
on 4 Jul 2011
I'm sorry about this one - it's somewhat over the top, and I promise I won't do any more. However, since I think it's a different approach to the others (arithmetic operations but no powers of 10!), here it is:
[ones(1, sum(x)==9*length(x)) x(1:length(x)-sum(cumsum(fliplr(x)) == 9*(1:length(x)))-1) repmat(x(max(1, length(x)-sum(cumsum(fliplr(x)) == 9*(1:length(x)))))+1, 1, sum(x)~=9*length(x)) zeros(1, sum(cumsum(fliplr(x)) == 9*(1:length(x))))]
0 Comments
See Also
Categories
Find more on Shifting and Sorting Matrices in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!