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# D1 Dijkstra - Can we repeat nodes? watch

1. I was doing the June 2015 D1 paper and was wondering why can we repeat nodes in the algorithm for 3.C

It says find the route but the answer in the mark scheme repeats a node, but I thought a route by definition could not repeat nodes.

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2. Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

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Just quoting in Puddles the Monkey so she can move the thread if needed
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(Original post by Puddles the Monkey)
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3. (Original post by thebobby)
I was doing the June 2015 D1 paper and was wondering why can we repeat nodes in the algorithm for 3.C

It says find the route but the answer in the mark scheme repeats a node, but I thought a route by definition could not repeat nodes.

Attachment 549343549345
You are correct in that Dijkastra's algorithm does not allow the repetition of nodes, but.

Part c is using Dijkstra's algorithm twice: Once when going from A to E, and once when going from E to J. There can be overlap between the two parts, but within each part a node only appears once, at most.

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Updated: June 16, 2016
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