Why doesn't recursion in my mergeSort algorithm work?

2022 10 7
1 个回答
回答已采纳
更新时间：2022 10 7
3 次查看（30 天）

0 个投票

I am following a book on algorithms and want to implement mergeSort myself. The problem is that I cannot get the desired ordering of my input array Arr. Have debugged and seen the problem but can't find a solution [which is that anything after mergeSort(Arr, p, q) is not executed at all]. In other languages like C, this would execute fine. Is there something missing [with respect to MATLAB] that will get the recursion to work?
function [sortedA] = mergeSort(Arr, p, r)
if p < r
q = floor((p + r)/2);
mergeSort(Arr, p, q);
mergeSort(Arr, q + 1, r);
merge(Arr, p, q, r);
end
sortedA = Arr;
end

请先登录，再回答此问题。

 采纳的回答

Jethro Djan
Jethro Djan 2022-10-7
编辑：Jethro Djan 2022-10-7

0 个投票

Apparently I didn't realise the fundamental error in my assumption which is that when dealing with arrays (or vectors in the case of MATLAB), I don't have default access to manipulating the pointers as would be in C. I have to deal with arrays by copying them around.
Edit: In case anyone is wondering what I ended up doing, it was something like this:
function [sortedA] = mergeSort(Arr, p, r)
if p < r
q = floor((p + r)/2);
leftArr = mergeSort(Arr(p:q));
rightArr = mergeSort(Arr(q+1:r));
sortedA = merge(leftArr, rightArr);
end
end

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Steven Lord
Steven Lord 2022-10-7
That is correct. Numeric arrays in MATLAB behave like value classes, not handle classes. See this documentation page for more information.

请先登录，再进行评论。

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 Structures 的更多信息

产品

版本

R2022a

标签

Community Treasure Hunt

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

Start Hunting!

Translated by