Wrong output for strand sort algorithm

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mustafa
mustafa 2023-5-31
评论： mustafa 2023-6-9
This sorting code depends on strand sort algorithm but when I enter input for example v1=[5,9,13,24,1,6] wrong output given(ans=5;9;13;24;5;9;13;24;1;6). Furthermore, matlab do not give any error but warning which indicates preallocating. How can I amend this code?
function result=myystrandsort(lst)
if length(lst)<=1
result=lst;
return;
end
result=[];
sorted=[];
while ~isempty(lst)
sorted(end+1)=lst(1);
lst(1)=[];
it=1;
while it<=length(lst)
if sorted(end)<=lst(it)
sorted(end+1)=lst(it);
lst(it)=[];
else
it=it+1;
end
end
result=[result,sorted];
end
result=result(:);

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回答（2 个）

Aman
Aman 2023-6-1
Hi Mustafa,
There are a few corrections to be made in your code:
  • You are not clearing the sorted array after the inner while loop, which is causing the elements to reappear in the result. To fix this, you can define the sorted array inside the while loop like this:
while ~isempty(lst)
sorted=[];
sorted(1)=lst(1);
lst(1)=[];
it=1;
  • Additionally, you cannot merge result and sorted arrays directly, since both arrays are sorted, you need to merge them in a sorted manner.
Hope this helps!
Harsh Saxena
Harsh Saxena 2023-6-1
Hi Mustafa,
There are mainly two problems with the code:
  1. Sorted list needs to be empty after every iteration of while ~isempty loop.
  2. You need to merge the list in sorted order.
function result=myystrandsort(lst)
if length(lst)<=1
result=lst;
return;
end
result=[];
while ~isempty(lst)
sorted = [];
sorted(end+1)=lst(1);
lst(1)=[];
it=1;
while it<=length(lst)
if(sorted(end)<=lst(it))
sorted(end+1)=lst(it);
lst(it)=[];
else
it=it+1;
end
end
result=merge_sorted(result,sorted);
end
result=result(:);
end
Here the merge_sorted function can be created as follows:
function outArray = merge_sorted(in1,in2)
inAll = [in1(:); flipud(in2(:))];
N = numel(inAll);
iFront = 1;
iBack = N;
outArray = zeros(N,1);
for iOut = 1:N
if inAll(iFront) <= inAll(iBack)
outArray(iOut) = inAll(iFront);
iFront = iFront+1;
else
outArray(iOut) = inAll(iBack);
iBack = iBack-1;
end
end
end
Hope this helps!
  1 个评论
mustafa
mustafa 2023-6-9
You saved my life mate.I am appreciate for your help, I can not thank you enough.

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