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The definition and description use the term "value", and some of the code examples use the term "key". I believe they are interchangeable in this article. We should pick one and be consistent. I propose we pick "key". I think it is more precise. Does anyone know what a tree with duplicate sort values looks like? Shouldn't the definition of BST be that every node's right subtree has values greater than or equal to the node's value?
The current definition says it's strictly greater, which isn't the case. Here is an excerpt from the lecture I once took at UC Berkeley: The full lecture can be found here http: I've also verified this with my reference book on algorithms.
By this definition self-balancing binary search trees are not binary search tree. Consider an empty AVL tree and insert three equal values. After the rotation there are equal values to both sides of the root node. So you either need to exclude equal values from binary search trees or allow equal values to both sides of a node. The right subtree of a node contains only values greater than or equal to the node's value. It is confusing that the article starts by claiming that equal nodes should always be in the right subtree, while the example image puts equal nodes such as the seven, which equals the root in the left subtree.
Why does the blurb about Optimal BSTs have a reference to "section Is this text copied and pasted out of a book? Is this a c violation? Yes - thank you very much. I see a few other minor flaws in the algorithm on the page. If you are deleting a leaf node, you must remove the link from the parent of that node to the node itself.
I also think that the delete method as it is implemented would cause an error, because you are deleting the node and then trying to get data from it Slightly off topic, but could the python examples be made clearer by the use of exceptions instead of returning numbers eg.
C is the appropriate choice here. I can't understand the "Traversal" example because I don't know what "callback" is or does. An example in another language is needed.
This seems like a discussion without proper arguments. People prefer different languages. I find Python more readable. I don't think the article should have any examples in concrete programming languages. Pseudocode should be more than enough, this is an encyclopedic article, not a coding cookbook. I think we should try making it as easy to understand for non-computer-scientists as reasonably possible.
Blocks of code don't really help with this objective. It seems to me this article details the same concept as Binary search algorithm. I suggest a merger. He Who Is The deletion algorithm should check for the case of both left and right being NULL before checking either side. No, the code works fine - I tested it. I worked on understanding the code in the article and found some issues.
I described them on my blog, see http: I hate to keep just pasting code around like this, but here's my take on the C version of removeNode. Tiger of Doom talk I implemented a recursive delete function - since BSTs are recursive abstractions I think that the deletion function in the article should use recursion.
We can then use a dynamic programming solution, detailed in section Cormen Sec Edition, to construct the tree with the least possible expected search cost. I wish that someone who has the book or has a nearby library from which he can borrow it could take the time to write about it. Since both the successor and the predecessor must have fewer than two children, either one can be deleted using the previous two cases.
In a good implementation, it is generally recommended to avoid consistently using one of these nodes, because this can unbalance the tree. I disagree with this.
Depending on which side of a node the equal values go to left or right , you can only base this deletion schema in predecessor OR sucessor not arbitrary. There are cases where taking the wrong choice will make equal values appear to the side they shouldn't be in.
I'm just wondering whether the example code for Deletion is correct The example seems to fail when the deleted key is not found in the tree.
It also acts differently than the upper image the example deletes the minimum of the right side, where the image deletes the max of the left side. I'm a student at Cal Poly State University San Luis Obispo, and as part of a class on teaching technical subjects we were asked to find an article that was unclear or otherwise inaccessible for the wider audience and clarify it, with an emphasis on improving understanding from a teaching point of view.
Feel free to reintegrate that information if you'd like, but in my opinion it doesn't belong in this article, or if it does it belongs in it's own section. My wiki markup skills are not very good, so feel free to correct any incorrect wiki-links I may inadvertently create. I've done my best to make them at least link somewhere correct, but I can't get the hang of linking to sections in other articles.
So the image can contain one or more duplicated values, to show where they go. I am asking senior wikipedia editors to approve this link and add it to the current article. I also made the intro clearer. I am pretty sure the code is correct, but any tips would be helpful. What if either value is NaN? Hi, What do you think of adding an observations section with regard to the data structure? Another observation is how to get the next or previous.
What about modified structures where the root contains the 'count', or has 'max' and 'min' fields, so it can have fewer operations in such cases? So should I edit away? I don't have much background in CS, but I wrote a binary-tree vocabulary once. The Python code assumes a parent pointer. The definition of a BST does not include a parent pointer. It seems that there is disagreement in the definition of a binary search tree.
The article currently says that there must be no duplicates and there are sources online that back it up , but many standard implementations of BSTs support duplicates, and Nick Parlante, at Stanford, says that they can contain duplicates http: If these rules are broken then the invariant associated with the bst breaks. You can effectively think of a bst as a concrete implementation of the abstract data type Set. The code checks the validity of BST is, in my opinion, wrong.
At least, clarification should be added. Second, it seems like these fields should be vice versa i. This sentence, and the paragraph it appears in, suffer from a rather unfortunate choice of concepts to explain orders and comparisons.
Making a distinction between less-than and comparison functions is language-specific; in languages with operator overloading, it can lead to circular definitions because less-than in fact has to be implemented in terms of what this paragraph calls a "comparator". I've been wanting to write something about this, but couldn't get my sources together, so I'll dump my thoughts here for now in the hopes that others can help. It is possible to implement the insert, delete and lookup operations in terms of two helper routines:.
With these, it is also possible to implement union, intersection and set difference much more efficiently than by just running repeated insertions, lookups and deletions. The symbol TreeNode is used in the article twice in different sense. The second case is a struct defined in Binary search tree Verification. There appears to be some differences in the introduction and the other sections of the article relating to balancing. From my reading the article seems that both balanced and unbalanced are claimed.
I may have read it wrong. From the B-Tree article: From the Types section: It is unbalanced and, in the worst case, performance degrades to that of a linked list. I have just modified 2 external links on Binary search tree. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information.
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