I have a list of many objects. Further, I have an additional group of lists consuming those objects. It's a strict rule that any given object either belong to the main list, or one of the other lists.
In general, the main object contains a master list of objects. Further, this main object also has its own concept of grouping these objects together into any separate arbitrary list.
I'd like to be able to query a list of those objects which are not currently a part of any of the other lists. I can naturally assume that I can synchronize a dedicated list of these objects, but that's not how I need to approach this. Instead, at any given time, I need to be able to fetch a list of those objects which are NOT a part of any of those group lists.
Another way put, out of that big giant list of all possible objects, I need to be able to iterate one by one through those which are NOT a part of any of the other group lists. Identifying whether it's a part of one of those lists is easy. But how do I fetch a list of items which are NOT a part of any group?
Specifically, without creating a whole separate list. I intend to use this main list of objects, yet filter out those objects which are a part of any given sub-list of objects.
More specifically, I need to be able to traverse through the list of objects which are not a part of any other list. I'd hate to keep track of a totally separate "ugrouped" list. I'd rather use the main list, and iterate each object in order in the list, while skipping over those objects which are part of the sub-lists.
For example, let's say I have a master list of 100 widgets. Only 30 of those have been categorized into some specific group list. The other 70 objects need to still be accessible by querying a list.
I'm looking for a loop something like...
for X := 0 to UngroupedObjectCount-1 do begin
O:= UngroupedObjectByIndex[X];
//TODO: Do something with O
end;
Related
I keep retrieving the entire LIST of Customer's Total Amount instead of the Specific Customer. I have tried using SELECT according to their Order ID to filter out other Customer. However, the result is still the whole list.
My code here
I have tried to FILTER using Customer Name and Order ID. However, the outcome is still the same, returning the entire LIST of Total Amount.
If you reference connect your line items to your order, app sheet will natively create a reverse reference on the order table that contains a list of all of the corresponding line items for that order.
The list that you're looking for lives in the data inside that column. To get the data out you need to do a list the reference, which will extract the value of whatever column you specify out of that reverse reference, creating a list of the values you want from those child records.
Then if you wanted to create a total for all of those line items, you could wrap that list dereference in sum().
References are the key to making just about everything advanced work inside app sheet, definitely worth wrapping your mind around.
Suppose you have a list of items (instructions in a function, posts on a blog, episodes in a TV series etc) that need to be kept in order, what is the recommended way to store them in Neo4j? Two possibilities that come to mind:
Assuming the items don't already have a suitable property for sorting by, assign them incrementing sequence numbers.
Use a linked list of nodes.
Which of these is typically recommended? Or is there a third option I'm missing?
Use a linked list.
Sequence numbers still have to be sorted, which is unnecessary overhead. And to do the sort, neo4j has to iterate through every node in the sequence, even if you are only interested in a small part of the sequence.
It is pretty common for a web application to display a list of items and for each item in the list to indicate to the current user whether they have already viewed the associated item.
An approach that I have taken in the past is to store HasViewed objects that contain the Id of a viewed item/object and the Id of the User who has viewed that item/object.
When it comes time to display a list of items this requires querying the database for the items, and separately querying the database for the HasViewed objects, and then combining the results of these queries into a set of objects constructed solely for the purpose of displaying them in the view.
Each e.g li then uses the e.g. has_viewed property of the objects constructed above.
I think it is time to find a better approach and would like to know what approaches you would recommend.
i wanna to know whether there is better idea also.
Right now my solution is putting the state in the redis and cached the view with fragment cache.
I am trying to change the index of a node, because there are some specific nodes that at all times needs to be at the bottom of my tree. I tried to change the Node.Index, but that did not change anything. So my question is: How do I change the Index of a PVirtualNode?
Thanks! - Jeff
To change the index of node A, find the node B that has the index you want A to have, and then call Tree.MoveTo(A, B, amInsertBefore, False). B and everything after it will shift down by one to make room for A, and their Index fields will be recalculated. This works even if A doesn't yet exist in the tree (such as just after calling MakeNewNode).
If you're using Index to associate each node with its corresponding data value in a list or array, then you'll find this largely ineffective for re-ordering the displayed values.
You canot change the index of a node. Normally when using VirtualStringTree you hold your data in your own data structure separate from the tree and access the data from the events.
You can also store data directly in the nodes (using a record), but I prefer the other approach because it keeps the logic out of the tree view.
For example, you could store the data in a list and access this list in the GetText handler (you can use Node.Index). Then, if you want to reorder the items, just reorder your list and everything else will happen automatically (you might have to call Invalidate on the tree).
Pseudocode:
Initializing:
Tree.RootNodeCount := MyList.Count;
In the GetTextevent:
NodeText := MyList [Node.Index];
Reordering:
Reorder (MyList);
Tree.Invalidate;
Given that you are still using the tree view control as a container, the ideal solution offered by Smasher is not available to you.
One rather obvious solution, given that your tree view has no hierarchy (i.e. it's a list) would be to use the Sort method with your own compare function (OnCompareNodes).
The other blindingly obvious strategy would be to add the node that you want at the bottom last. If you need to add other nodes later, then insert them above the special last node with InsertNode. This simple approach will probably suffice for the problem as you have described it.
TVirtualNode is a doubly-linked list, it's not a index-based structure: you change the index of a node by removing it and adding it where you want it.
Look into DeleteNode and AddChild.
Given two linked lists of integers. I was asked to return a linked list which contains the non-common elements. I know how to do it in O(n^2), any way to do it in O(n)?
Use a hash table.
Iterate through the first linked list, entering the values you come across into a hash table.
Iterate through the second linked list, adding any element not found into the hash table into your list of non-common elements.
This solution should be O(n), assuming no collisions in the hash table.
create a new empty list. have a hash table and populate it with elements of both lists. complexity n. then iterate over each list sequentially and while iterating, put those elements in the new list which are not present in the hash table. complexity n. overall complexity=n
If they're unsorted, then I don't believe it is possible to get better than O(n^2). However, you can do better by sorting them... you can sort in reasonably fast time, and then get something like O(nlogn) (I'm not certain that's what it would be, but I think it can be that fast if you use the right algorithm).