kandi X-RAY | SkipList Summary
kandi X-RAY | SkipList Summary
Skip lists are data structures that use probabilistic balancing rather than strictly enforced balancing. As a result, the algorithms for insertion and deletion in skip lists are much simpler and significantly faster than equivalent algorithms for balanced trees. 跳表是90年代由William Pugh发明的一种概率平衡数据结构。跳表的平衡是一种基于随机的非严格平衡。它完全基于链表实现，而不涉及树的结构，和普通的平衡树相比， 跳表的新增和删除操作实现相对简单很多。跳表的核心思想就是将扁平的列表进行分层，每个节点在插入的时候会生成一个随机的层数，基于此随机的层数与跳表中相邻的数据连接。 跳表的增删改查操作具有O(log N)的均摊复杂度。.
Top functions reviewed by kandi - BETA
- Associates the specified value with the specified key
- Generate a random level
- Compares the given key with the given key
- Links a node at a given level
- Convenience method to check equality
- Returns null if the node is not a data node
- Check if a node is a data node
- Finds the node with the given key
- Returns the highest key currently active
- Returns the last node
- Creates an iterator for the value iterator
- Returns an entry iterator over the entries in this node
- Returns the lowest key currently present in this skip list map
- Gets first node
- Removes the mapping for the specified key from this map
- Deletes a node
- Returns the value associated with the specified key
- Returns true if the map contains the specified key
- Returns an iterator over the keys in the cache
SkipList Key Features
SkipList Examples and Code Snippets
Trending Discussions on SkipList
I study the implementation of Redis, I know that there are two data structure (
zset. I know some basic idea of
skiplist (keep multiple pointer to access next element faster, avg time complexity of search is O(logN)).
My question is :
I read the info said that there are two situations that Redis will use
skiplist to implement
zset, first : there are many members in zset, second : memebers in
zset are long
What's the benefit to use
skiplist instead of
ziplist in these two situations, why these two situations need special treatment? Why don't we always use one data structure to implement
ANSWERAnswered 2021-Apr-02 at 08:36
ziplist is O(n) time complexity for searching and updating and skiplist is O(logN)
The only benefit for ziplist is memory usage. As zip list implement by linear memory address and no pointers to other nodes, it can save a lot of memory space for Redis.
When you only have few members in zset, O(N) and O(logN) will not have significant difference. But memory usage will have huge differences(consider you have 1m keys of zset and each zset only have 10 members).
And when there are a lot of members in zset(like 1m), time complexity is important since it will affect the concurrent performance.
I have a DXL script that open (read or edit) modules and put them in a skip list (so that I could close them at the end)
The skip list store the module handle of each module read or edit :...
ANSWERAnswered 2021-Mar-30 at 16:05
Not sure if this is due to the excerpt you posted, but you should always turn off the autodeclare option and ensure that you always use the correct types for your variables by either checking the DXL manual or by using alternative sources like the "undocumented perms list" .
data performed on a
ModuleVersion returns type
Module. So you already have what you need. An alternative would be the perm
bool open(ModName_ modRef). And note that the perm
module does not return a
Module, but a
Also, in addition to
bool isRead(Module m),
bool isEdit(Module m) and
bool isShare(Module m)(!!) when you really want to close modules that have been opened previously, you might want to check
bool unsaved(Module m)
When I tried to implement the SkipList by rust, I was trapped by the implement of
Rc>. Code is listed:
ANSWERAnswered 2021-Feb-27 at 15:02
Is there a elegant implement of the Iterator for the Rc in Rust?
Not really. There's two big things in your way.
One limitation when building an
Iterator is that the output type cannot reference the iterator itself. It can either return an owned value (no lifetimes involved) or return references bound to the lifetime of some other object.
I see you've tried to communicate that you want to return
Refs bound to the lifetime of the orignal
SkipList by using
PhantomData<&'a K> and also using
'a in your
Iterator::Item. However, since your iterator can only source values from
ptr, an owned value with no lifetime-linkage to
'a, the compiler will complain about mismatched lifetimes at one point or another.
In order to do this, your iterator would have to use something bound to
'a, probably some form of
However, another limitation is when you have nested
RefCells, with each level that you iterate, you need to keep around an additional
Ref. The reason being that borrows from a
Ref don't keep the lifetime of the
RefCell, but from the
how can I remove an element from a list if it only contains components. Or how can I bet a wildcard?
i want remove '+03+ [ NEW INFO WILL RESOLVE TO TILL ]+' in test, wehen 'new' from skiplist match is...
ANSWERAnswered 2021-Jan-30 at 17:40
wiht list comprehension:
Below is my skiplist implementation, The code working fine, but what I need this that when key matches with the existing key in then value to be updated with the new value, but in my case the item inserted twice and the data is not replaced. I want to implement this at the time of update so that i do not have to search the entire list.
Any help in this regard is highly appreciated...
ANSWERAnswered 2020-Oct-11 at 18:13
If you want your code to be able to update existing elements when inserting a new value, then you have to combine the searching you do in
containsSkipList() with the creation of a new
Only difference I understand is between iterators.
SkipList has weakly consistent, while
TreeSet has fail-fast. Other than that I don't see any synchronized methods inside
SkipList (although it is in Concurrent package).
Can someone please explain to me how is
SkipList concurrent when it doesn't have any synchronization in it? What problems can it help me with and why should I ever use it other than this difference between Iterators?
ANSWERAnswered 2020-Aug-23 at 16:52
„…how is SkipList concurrent when it doesn't have any synchronization in it?…“
ConcurrentSkipListSet is concurrent because the elements it holds cannot be written to at the same time by concurrently executing threads. It achieves its concurrency without using
synchronized and locks.
The long version
Concurrency in the context of the concurrent collections, does not necessarily mean those classes all implement thread safety using monitors (aka, the
First you should understand that thread safety is essentially about ensuring that two or more competing threads do not modify the shared state of an application. Then you realize that there are ways (some more performant) other than
synchronized to achieve thread safety.
Making sure your state cannot be modified (that it's immutable) in the first place is one simple but very effective way to get thread safety.
Also, a class can be thread safe by delegating its thread safety responsibilities to a different, thread-safe class.
ConcurrentSkipListSet is considered to be concurrent because, as its Javadoc says, its: „Insertion, removal, update, and access operations safely execute concurrently by multiple threads“.
It achieves its concurrency because it delegates its thread safety responsibilities to a thread-safe class; namely:
ConcurrentSkipListSet is thread-safe because
ConcurrentSkipListMap is. And
ConcurrentSkipListMap is thread-safe because, by using
AbstractMap.SimpleImmutableEntry internally, it guarantees that none of its state (its keys and values) can be modified by currently executing threads, because its state is immutable.
You can see
ConcurrentSkipListSet delegating to
ConcurrentSkipListMap at several places in the source code I linked to above. If you're interested in learning more about delegating thread safety, I recommend you read Chapter 4, Composing Objects, Java Concurrency In Practice.
„…What problems can it help me with“
Using it gets you free thread-safety. The kind that is way more performant — and with way less risk of shooting yourself in the foot — than using
„…why should I ever use it other than this difference between Iterators?“
If the state of your application needs to be stored in some collection and that collection will be accessible in any way to concurrently executing threads, then using
ConcurrentSkipListSet is a thread-safe option that you have.
I want a generic function that can instantiate object of a few different
enum types I have by supplying the enum type and the
Int raw-value. These
enums are also
I tried this:...
ANSWERAnswered 2020-Mar-27 at 11:04
The issue is that
T.RawValue can be something else than
Int with your current type constraints. You need to specify that
T.RawValue == Int in order to pass your
rawValue: Int input parameter to
So I'm trying to implement a FastDefaultList class which is basically a skiplist that represents an infinite list with indices 0,1,2,3,…,∞. At the start, every value in this list is assigned the default value null. Otherwise, this class behaves just like a List; it has the add(i,x), remove(i), set(i,x), and get(i) that behave just like the same methods in a list. Each of these operations should run in O(log n) time. A lot of my skiplist code comes from:
I think I have most of it working for the most part but I'm trying to fix my get() and set() methods. Whenever I try to compile the program I get the error:
error: no suitable method found for add(int,FastDefaultList.Node,int) add(i, node, 0);
and I'm not sure why. Any help would be appreciated....
ANSWERAnswered 2020-Mar-13 at 17:37
Your add function is accepting 2 params
Of, so my frustration levels have gotten to the point that I must reach out for assistance.
I have a single file that uses pandas to read a report and do some data manipulation. I have it completed and would like to create a stand alone exe for it.
Unfortunately, Pandas is not "out of the box" able to be used when you are creating an executable as i get an error stating : ModuleNotFoundErrer: No Module named 'pandas'
I went online and looked up solutions, and so far I have done ALL OF THIS:
Edited the EGTReport.spec file:...
ANSWERAnswered 2020-Mar-06 at 09:56
I guess you have problem with installation of pandas module. Try to run command "pip install pandas" first may be your pandas package is not install. then you can run pyinstaller.
However you can do additional things like setup settings follow below example:
Please fill "install_requires" whatever packages you want.
We're learning about skiplists at my university and we have to find k-th element in the skiplist. I haven't found anything about this in the internet, since skiplist in not really a popular data structure. W. Pugh in his original article wrote:
Each element x has an index pos(x). We use this value in our invariants but do not store it. The index of the header is zero, the index of the first element is one and so on. Associated with each forward pointer is a measurement, fDistance, of the distance traversed by that pointer:
x→fDistance[i] = pos(x→forward[i]) – pos(x).
Note that the distance traversed by a level 1 pointer is always 1, so some storage economy is possible here at the cost of a slight increase in the complexity of the algorithms.
ANSWERAnswered 2018-May-01 at 20:40
I'm going to assume you're referring to how to find the
k-th smallest (or largest) element in a skip list. This is a rather standard assumption I think, otherwise you have to clarify what you mean.
I'll refer to the GIF on wikipedia in this answer: https://en.wikipedia.org/wiki/Skip_list
Let's say you want to find the
k = 5 smallest element.
You start from the highest level (4 in the figure). How many elements would you skip from
6 (we also count the
30). That's too much.
Go down a level. How many skipped from
So we reduced the problem to finding the
k = 5 - 2 = 3 smallest element starting at
50 on level
How many skipped from
4, that's one too many.
Go down a level. How many skipped from
2. Now find the
3 - 2 = 1 smallest element starting from
70 on level
How many skipped from
2, one too many.
90 on level
1 (itself). So the answer is
So you need to store how many nodes are skipped for each node at each level and use that extra information in order to get an efficient solution. That seems to be what
fDistance[i] does in your code.
No vulnerabilities reported
You can use SkipList like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the SkipList component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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