dual kd-tree construction

Please anyone tell me how to construct dual kd-tree and how to traverse it?

And at least tell me the algorithm for finding nearest neighbor using this 开发者_开发技巧dual tree concept in java. This will help full for my project.

Thank you.

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If you can read Python, look at the clear source for query_ball_tree described in scipy.spatial.KDTree,
"Find all pairs of points whose distance is at most r". (Is that what you want to do ?)