存储二进制路径的最有效方式（例如通过二叉树）

Question

I am trying to store a binary path as efficient as possible (in terms of using as little memory as possible/necessary). A path that leads to a specific node in a linked binary tree (beginning at the root), for example -- An easy way to store this would be to store the nodes (or their values) themselves.

But this is not efficient, nor is it elegant. If I want to apply the same path on a different BinaryTree, this does not work.

So You could save just a sequence, eg a string, like "lrllrrr" where l means left branch, r means right branch. But storing this information in a string is still not very efficient.

This can be improved by using an array of booleans. But I don't know how those are handled in Java in the backgrund. Also, I would like to avoid fixed-sized Strings/Arrays.

My next idea was to directly store the path in a binary integer like 0100111 (reading left to right). You could then add a 'move left' by using << and a 'move right' by using << , followed by ++ . But this approach has three weaknesses:

1. In Java, there are no unsigned integers. I don't know much about bitwise operators in Java, so I am wondering about how to deal with the sign bit of a primitive int or long ?
2. The entry count of such a representation is limited by the number of binary digits that make up an integer (eg 63 for a long ). That can probably be solved by using BigInteger .
3. A path that starts with at least one 'left' entry cannot be stored correctly, because '0' Digits on the very left are ignored by default when dealing with integers.

So, is there any way in Java to store a specific series of bits so that i can read them individually without much effort? If something like this does already exist I'd like to read more about how it is immplemented. If there is no such thing in Java and it is too difficult or simply impossible, how would you approach that in another environment/ in another language?

Thanks in advance.

EDIT : '0' Digits on the very left

Answer 1

You can use a single integer to signify the path. The tree increases in size 1,2,4,8 etc

Also note that when talking about "smallest", keep in mind memory block size constraints, and also be aware that your binary tree is probably going to be much larger than your path representation.

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Answer 2

摘自@RealSceptic 的评论： BitSet对我来说很好用。