Sorting algorithms with requirements

Question

I am looking for an algorithm that can do sorting with requirements. As an example if I have 3 nodes N1, N2 and N3 I have the requirement that N2 must come after N3, and N3 have the requirement that it must come after N1. So the correct sort will be N1, N3, N2.

en.wikipedia.org/wiki/Topological_sorting

Timothy Shields
– Timothy Shields

2014-06-07 05:34:09 +00:00
Commented Jun 7, 2014 at 5:34 — Timothy Shields
– Timothy Shields, Commented Jun 7, 2014 at 5:34

Timothy Shields · Accepted Answer · 2014-06-07 05:40:43Z

5

Form a graph from your requirements. Your items are the nodes and there is a directed edge from A to B if A must come before B. Repeatedly, remove a node that has no incoming edges and remove all of its outgoing edges. Do this until you have removed all the nodes. You will have removed them in the desired order, satisfying the requirements.

For the details of the implementation, see here: Topological sorting.

answered Jun 7, 2014 at 5:40

Timothy Shields

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