Talk:Non-continuous subsequences

Question: How does D's algorithm make sure not calculating the same subsequence twice?

This is the algorithm description in D session:

from the original sequence, select some continuous subsequences of length >= 3,
from each continuous subsequences in (1), remove some in-between elements beside first and last element,
each subsequences some elements removed in (2) is a non-continuous subsequences.

Explanation:

I assume the order in task description mean index order(or position of elements in a sequence/list), so that values of element is not relevant to order, not need to be sorted, nor need to be comparable <Just read the remark in the bottom of D session. This part of comment is not necessary, but may keep as a record of discussion -- badmadevil 05:24, 29 March 2008 (MDT) >;
each subsequence in (1), or contseq in D's example code, is uniquely determined by its head element index and tail element index;
when removing elements from contseq in (2), the elements indexed by head and tail is not touched, so each non-continuous sequence produced by this contseq will not overlap with other non-continuous sequence produced by another contseq, since they must have different pair of head/tail indexs;
within those non-continuous sequence produced by the same contseq, if they have been taken out different numbers of elements, they are of course different non-continuous sequences, because they have different number of elements ;
for those non-continuous sequence produced by taken out same number of elements from the same contseq, the uniqueness of non-continuous sequences is supported by uniqueness of set of index of elements to be removed ( removeIndexs in D's code) produced by Combi iterator.

I've not got a formal training in computer science, please try to understand casually, thank you. -- badmadevil 05:05, 29 March 2008 (MDT)

Looks good. I understood the "beside first and last element" incorrectly, my fault. If you don't mind, I've changed the wording of your explanation in the example a bit. --Dirkt 07:31, 29 March 2008 (MDT)

Of course not mind -- badmadevil 09:04, 29 March 2008 (MDT)

Suggestions for improvement

After this post in the RC blog, I ended up here and thought the page could be improved if references to algorithms attempted where added to the tail of the task description and implementations referred to which they were following. --Paddy3118 06:08, 12 May 2009 (UTC)

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