Check if element in array are square of each other

7 views (last 30 days)
Hello,
I have a problem where I have to find possible squares in an array. For example [7 5 49] or [49 5 7] is true since 7 squared is 49, but [11 13 25] should return false.
Is there a way to do it better than a nested loop?
Thank you!
function y = isItSquared(x)
y = false;
for i = 1:length(x)
for j = i+1:length(x)
if x(i)^2 == x(j) || x(i) == x(j)^2
y = true
break
end
end
end

Accepted Answer

Mark Sherstan
Mark Sherstan on 22 Mar 2019
You can get rid of one of the for loops:
function y = isItSquared(x)
y = false;
xSquare = x.^2;
for ii = 1:length(x)
if (sum(x(ii) == xSquare) ~= 0)
y = true;
return
end
end
  4 Comments
am
am on 22 Mar 2019
So if xSquare has no index, it means that the whole array is checked?
sum(x(ii) == xSquare) ~= 0
Mark Sherstan
Mark Sherstan on 22 Mar 2019
Correct, it is a boolean check returning an array of 1's or 0's.

Sign in to comment.

More Answers (4)

madhan ravi
madhan ravi on 22 Mar 2019
nnz(V.^2==V.')>=1 % where V your vector, result 0 means false, 1 means true
  5 Comments
madhan ravi
madhan ravi on 22 Mar 2019
Edited: madhan ravi on 22 Mar 2019
@eq means equal ,see https://in.mathworks.com/help/matlab/ref/bsxfun.html for further explanation.
https://in.mathworks.com/help/matlab/ref/nnz.html - nnz() gives you the total number of non-zero elements.
>= means if you have one or more then set it to true.
So what happens is each element of the vector is compared with the square of each element , so if atleast a single match is found then the answer returned is 1 meaning true.
am
am on 22 Mar 2019
I think it was a fantastic answer as well, thank you!

Sign in to comment.


Steven Lord
Steven Lord on 22 Mar 2019
I would probably do this using some subset of the ismember, any, sum, all, and/or isequal functions. Read through the help text and see if you can think of a way to use some of those functions to accomplish that task.

KSSV
KSSV on 22 Mar 2019
a = [7 5 49] ;
b = [49 5 7] ;
idx = a.^2==b
In idx if 1 , true, if zero false.

Agam Sharma
Agam Sharma on 8 Jun 2022
function b = isItSquared(a)
b=false;
c=a.^2; %creating another array containing respective squares in 'a'
for i=1:length(c)
if(ismember(c(i),a)) %check if square is present in a itself
b=true;
end
end
end

Categories

Find more on Loops and Conditional Statements 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!