# What Mistake I am making in the code

3 views (last 30 days)
Manav Divekar on 4 Nov 2021
Answered: Steven Lord on 4 Nov 2021
I want to randomly pick two numbers from [39 25 91 71] swap it. and use while loop so that it swaps continuely until the vector is sorted. and display the sorted vector.
function out = sortbyrandomswaps(n)
x = 0;
y = 0;
while ~ all(diff(n)>=0)
x = n(randi(numel(n)));
y = n(randi(numel(n)));
x = a;
y = x;
a = y;
end
out = all(diff(n)>=0);

Yongjian Feng on 4 Nov 2021
Edited: Yongjian Feng on 4 Nov 2021
Maybe this:
sortbyrandomswaps([5 4 3 2 1]);
function out = sortbyrandomswaps(n)
while ~ all(diff(n)>=0)
idx1 = randi(numel(n));
idx2 = randi(numel(n));
a = n(idx2);
n(idx2) = n(idx1);
n(idx1) = a;
disp(n); % for debug only. Remove it if everything works.
end
out = all(diff(n)>=0);
end

Steven Lord on 4 Nov 2021
FYI you can perform a swapping operation in one step without needing an explicit temporary:
x = (1:10).^2
x = 1×10
1 4 9 16 25 36 49 64 81 100
toSwap = [4 7]
toSwap = 1×2
4 7
x(toSwap) = x(flip(toSwap)) % key step
x = 1×10
1 4 9 49 25 36 16 64 81 100
You could generalize this a bit if you wanted to swap a series of elements.
toSwap2 = [2 5 3 8 1];
x(toSwap2) = x(circshift(toSwap2, 1))
x = 1×10
64 1 25 49 4 36 16 9 81 100
The second element of x goes to position 5, the fifth to position 3, the third to position 8, the eighth to position 1, and the first to position 2.

R2021a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!