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POPython, recursive breadth first search
 

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  1. POPython, recursive breadth first search
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    <p>I am trying to find the shortest path on a grid(list of lists of tuples) I've gotten this so far:</p> <pre><code>def planPath(self, x, y, goal, board): visited = [] path = [] def pathFinder(curr): visited.append(curr) neighbors = None if curr == goal: visited.append(curr) return curr neighbors = [neighbor for neighbor in curr.neighbors if type(neighbor) is not Land.Water and neighbor not in visited] neighbors.sort(key=lambda neighbor: abs(neighbor.location[0] - goal.location[0]) + abs(neighbor.location[1] - goal.location[1]) + abs(neighbor.elevation - goal.elevation), reverse=False) </code></pre> <p>x, y are the current location, is obvious, and board is, well the entire board. The thought was that it would be recursive. For every call I would get the neighbors for the current node, filter out the water(untravelable) and the visited. Then sort by the closest to the goal. Next I want to go through and do a breadth first search. So I will expand all the neighbors, then expand each of their neighbors and so on. Each branch would go on until they have no neighbors, they would return None and be done with. Then end result being that the only one to return will be the first brach to reach the goal, i.e. the shortest. Does anyone know how I could do this?</p> <p>I was thinking this: </p> <pre><code>for neighbor in neighbors: next = pathFinder(neighbor) if next: visited.append(cure) return curr else: return None </code></pre> <p>but, correct me if I'm wrong, but that would result in depth first search, not breadth.</p>
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    1. PTQuestion
    1. USMartijn Pieters
    1. USEasilyBaffled
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    1. COYour indentation is all over the map (mixing tabs and spaces is never a good idea). I did my best to fix things, can you verify your post?
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      1. USMartijn Pieters
    2. COYup looks right. Thanks for the fix.
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      1. POPython, recursive breadth first search
      1. USEasilyBaffled
    3. CORecursion is not a natural fit for a breadth-first search. It makes much more sense if you're doing a depth-first search, since the call stack helps you keep track of the locations you've visited so far. For a breadth-first search you want to be using a queue instead. See [this related question](http://stackoverflow.com/questions/2549541/performing-breadth-first-search-recursively) for more discussion.
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