Most examples of BSTs I have seen are of the form
Class Node {
Node left;
Node right;
Key key;
Value value;
}
But BSTs looks like a specific form of Binary Heaps with a extra constraint , namely the left child value should be less than parent value which should be less than right node value.
Binary heaps are easily implemented using arrays. Why not create BSTs using arrays making sure that this extra rule is maintained ? What are the disadvantages of doing so ?
The answer is simple: You can't just dynamically change the size of an array.
The size of an array can't just be changed afterwards. If you would use an array you'd have to enlarge it or shrink it depending on what is added or removed which would cause unnecessary overhead since you would have to copy the content from the old array to the new array whenever you do that.
Using nodes that use references or pointers allow you to just (re)assign left and right to a new element accordingly whenever you insert or set it to null (or something similar) if you remove an element which gives you a much more dynamic structure.
Related
I'm trying to clear an array after each iteration of a for loop in LabVIEW, but the way I've implemented it has the values not going directly to what I want, but it changes with previous values in other parts of the array.
It isn't shown, but this code is inside of a for-loop that iterates through another numeric array.
I know that if I get the array to clear properly after each loop iteration, this should work. How do I do that? I'm a beginner at Labview but have been coding for awhile - help is appreciated!!!
[![labview add to array][2]][2]
It looks as if you're not quite used to how LabVIEW passes data around yet. There's no need to use lots of value property nodes for the same control or indicator within one structure; if you want to use the same data in more than one place, just branch the wire. Perhaps you're thinking that a LabVIEW control or indicator is equivalent to a variable in text languages, and you need to use a property node to get or set it. Instead, think of the wire as the variable. If you want to pass the output of one operation to the input of another, just wire the output to the input.
The indicators with terminals inside your loop will be updated with new values every loop iteration, and the code inside the loop should execute faster than a human can read those values, so once the loop has finished all the outputs except the final values will be lost. Is that what you intended, or do you want to accumulate or store them in some way?
I can see that in each loop iteration you're reading two values from a config file, and the section is specified by the string value of one element of the numeric array Array. You're displaying the two values in the indicators PICKERING and SUBUNIT. If you can describe in words (or pseudocode, or a text language you're used to) what manipulation of data you're actually trying to do in the rest of this code, we may be able to make more specific suggestions.
First of all, I'm assuming that the desired order of operations is the following:
Putting the value of Pickering into Array 2
Extracting from Array 2 the values to put in Pickering 1 and Pickering 2
Putting Array 2 back to its original value
If this is the case, with your current code you can't be sure that operation 1 will be executed be fore operation 2. In fact, the order of these operations can't be pre-determined. You must force the dataflow, for example by creating a sequence structure. You will put the code related to 1 in the first frame, then code related to operation 2 in the second.
Then, to put Array 2 back to it's original value I would add a third frame, where you force an empty array into the Value property node of Array 2 (the tool you use for pickering, but as input and not as output).
The sequence structure has to be inside the for loop.
I have never used the property node Reinit to default, so I can't help you with that.
Unfortunately I can't run Labview on this PC but I hope my explanation was clear enough, if not tell me and I will try to be more specific.
I'm new to Aerospike and am probably missing something fundamental, but I'm trying to see an enumeration of the Keys in a Set (I'm purposefully avoiding the word "list" because it's a datatype).
For example,
To see all the Namespaces, the docs say to use SHOW NAMESPACES
To see all the Sets, we can use SHOW SETS
If I want to see all the unique Keys in a Set ... what command can I use?
It seems like one can use client.scan() ... but that seems like a super heavy way to get just the key (since it fetches all the bin data as well).
Any recommendations are appreciated! As of right now, I'm thinking of inserting (deleting) into (from) a meta-record.
Thank you #pgupta for pointing me in the right direction.
This actually has two parts:
In order to retrieve original keys from the server, one must -- during put() calls -- set policy to save the key value server-side (otherwise, it seems only a digest/hash is stored?).
Here's an example in Python:
aerospike_client.put(key, {'bin': 'value'}, policy={'key': aerospike.POLICY_KEY_SEND})
Then (modified Aerospike's own documentation), you perform a scan and set the policy to not return the bin data. From this, you can extract the keys:
Example:
keys = []
scan = client.scan('namespace', 'set')
scan_opts = { 'concurrent': True, 'nobins': True, 'priority': aerospike.SCAN_PRIORITY_MEDIUM }
for x in (scan.results(policy=scan_opts)): keys.append(x[0][2])
The need to iterate over the result still seems a little clunky to me; I still think that using a 'master-key' Record to store a list of all the other keys will be more performant, in my case -- in this way, I can simply make one get() call to the Aerospike server to retrieve the list.
You can choose not bring the data back by setting includeBinData in ScanPolicy to false.
I am trying to build an XPath for a property that is constantly changing. The number prefix is bound to change sometimes.
Original:
//*[#id="MainContent_DXEditor3_I"]
which I can query using
$x('//*[#id="MainContent_DXEditor3_I"]
Intended use: I would like to build the string to handle any number in the sub-string. Example: if the property changes to 'MainContent_DXEditor33_I' or 'MainContent_DXEditor8_IXYZ' - I still want to be able to find the element without having to rebuild
You can try to relax the predicate by using starts-with() :
//*[#starts-with(#id, "MainContent_DXEditor")]
You should try to identify a unique parent of the element or save xpath as a string that contains a variable.
These are the 2 possible solutions.
A general selector will return multiple elements, if you identify a unique parent then you are closer and after that you can select any first, second.. last if you have a list.
We had the following code to retrieve data of type TYPE through a model, which is a custom proxy model. This is required by the next QSortFilterProxyModel to make the decision about filtering of elements. The code is actually combined from 2 functions: in the project we usually have some arbitrary index related to some ROW and use it to retrive the data from another predefined column which contains TYPE data.
QModelIndex index = sourceModel()->index(row, COLUMN1, sourceParent); /* sourceParent is always'invalid' - retrieving data from top-level items*/
ModelIndex sibling = index.sibling(row, COLUMN2);
return sibling.data(Qt::EditRole).value<TYPE>();
This worked fine with Qt4 but when moved to Qt5 sibling became 'invalid'. I wonder what has happened, taking into account that the data is actually there, which I see, by changing the code to the following
return sourceModel()->index(sourceRow, COLUMN2, sourceParent).data(Qt::EditRole).value<TYPE>();
-works fine
Looking at the implementation of sibling(), I cannot tell what makes it return an invalid index in your case. Comparing with the Qt4 implementation, maybe it's around the IndexMap use.
But why don't you simply use your solution with sourceModel()->index(sourceRow, COLUMN2, sourceParent), since it already seems to be what you actually want to do?
I am batch printing through many assemblies of AutoCAD documents. I have a recursive method that goes through each drawing to verify if it has any children, and then goes into each children to see if they have any children... and so on (recursively).
It has occured that I encounter a drawing that I has already printed, and it is completely useless for me to go through that drawing and print all it's children again.
So... I wanted to build a virtual list, if you will, of the exact replica of items in my tree view. I would use it to verify if the item I'm trying to print, already exists in the virtual list, if so ... then I would just insert the KeyValue in the tree, saving a lot of time.
I figured my declaration of my dictionary would look something like this ...
Dim dic_AllAssemblies As New Dictionary(Of String, TreeNodeCollection)
I took a screenshot for an example of my treeview:
The dictionary would contain the main top item "ADF020-080A0" as it's first key, and in that key the values of all it's children would be included ... Is that even possible? It might go down 6-7 levels or even more... Can a dictionary or ... list handle that? Or is there another method that I'm not yet aware of?
ADF020-080A0
ADF020-081A0
M17981
M17981
ADF000-092AS
Etc...
Etc...
I don't know any reason that would not work. With a Dictionary you have the .ContainsKey(string) to check for a duplicate key name. If the key is found, skip it.