Finding an A* heuristic for a directed graph

Posted by Janis Peisenieks on Programmers See other posts from Programmers or by Janis Peisenieks
Published on 2011-12-26T12:21:31Z Indexed on 2012/06/04 4:47 UTC
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language-agnostic

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graph-traversal

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heuristics

In a previous question, I asked about finding a route (or path if you will) in a city. That is all dandy. The solution I chose was with the A* algorithm, which really seems to suit my needs. What I find puzzling is heuristic. How do I find one in an environment without constant distance between 2 nodes? Meaning, not every 2 nodes have the same distance between them.

What I have is nodes (junctures), streets with weight (which may also be one-way), a start/finish node (since the start and end is always in the same place) and a goal node. In an ordinary case, I would just use the same way I got to goal to go back, but since one of the streets could have been a one-way, that may not be possible.

The main question

How do I find a heuristic in a directed graph?

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