heapify | fastest JavaScript priority | Runtime Evironment library
kandi X-RAY | heapify Summary
kandi X-RAY | heapify Summary
. A very fast JavaScript priority queue, implemented using a binary heap, which in turn is implemented using two underlying parallel typed arrays. No dependencies whatsoever; just plain, vanilla JS.
Support
Quality
Security
License
Reuse
Top functions reviewed by kandi - BETA
Currently covering the most popular Java, JavaScript and Python libraries. See a Sample of heapify
heapify Key Features
heapify Examples and Code Snippets
Lines of Code : 25License : Permissive (MIT License)
Copyprivate void minHeapify(int pos)
{
// If the node is a non-leaf node and greater
// than any of its child
if (!isLeaf(pos)) {
if (Heap[pos] > Heap[leftChild(pos)]
|| Heap[pos] > Heap[rightChild(pos)]) {
// Swap with t void heapify(int arr[], int n, int i)
{
int largest = i; // Initialize largest as root
int l = 2*i + 1; // left = 2*i + 1
int r = 2*i + 2; // right = 2*i + 2
// If left child is larger than root
if (l < n && arr[l] > a private void heapifyDown() {
// Step 1: Start from the root of the heap as the current node
int index = 0;
while (hasLeftChild(index)) {
// Step 2: Determine the largest node between the chil Community Discussions
Trending Discussions on heapify
QUESTION
My current implementation (shown below) works, but it's not in place. I tried to google, but I couldn't find an example. Your guidance is appreciated!
As you can see, in the second phase of sorting, I used sliced the original list so I can heapify this slice. However, I'm not supposed to use the slice operation as it creates a new list. What else can I try?
...ANSWER
Answered 2022-Mar-30 at 11:43You could take the following steps to make it inplace:
Make it possible for the heap to only act on part of a given list, ignoring the values that do not belong to this part. For that purpose, introduce a
sizeattribute, which starts with the same value aslen(contents), but can be reduced by the user of the heap. This means that you also need to:- Replace every use of
len(self), orlen(self._data)withself.size - Move the
is_emptymethod into the subclass, which actually removes the need to have a subclassing at all.
- Replace every use of
Replace the part where you create a new instance of a heap with:
QUESTION
Below is my implementation for Dijkstra's algorithm using heaps (for undirected graphs).
This works just fine for reasonably sized graphs however I am not satisfied by my code for recalculating greedy criterion of nodes connected to the newly explored node.
Here I iterate over all of the items in the heap which doesn't look like a good use of the data structure. Is there a better way to achieve this ?
The graph is a dictionary which contains for each node (key) a list of nodes connected to it and the length of the edge.
graph[v] returns [[w_1, l_1],...,[w_k, l_k]] where there is an edge between v and w_i of length l_i for all is between 1 and k. Sort of like an adjacency list.
ANSWER
Answered 2022-Mar-29 at 17:52There are several alternative implementations of Dijkstra's algorithm, but none of them need to iterate through the heap, nor remove arbitrary nodes from it, nor re-heapify it repeatedly. All those actions kill the performance benefit that a heap is intended to give.
I would also advise to avoid global variables. Instead pass what is needed as arguments, and let the function dijkstra return the results.
Here is one of the possible implementations you could use for your graph data structure:
QUESTION
I'm having hard time digesting this particular code block from java.util.PriorityQueue#initElementsFromCollection method.
...ANSWER
Answered 2022-Mar-23 at 09:15The constructor (or rather its author) does not trust the incoming collection. The collection’s toArray method could violate the contract and return a shared array rather than creating a new one. This way, the caller could get hands on the internally used array of the constructed PriorityQueue instance.
So, the constructor makes another defensive copy, except when the incoming collection is an ArrayList exactly, i.e. not even a subclass of it. In other words, it trusts the ArrayList’s toArray implementation to adhere to the contract, to skip the additional copying step in this specific case. That’s why not even a subclass of ArrayList will be accepted, as a subclass could have overridden the toArray method.
A similar mistrust has been displayed in the default implementation of Stream.toList() as discussed in this question and the comment section beneath that question.
The default implementation has been specified as
QUESTION
Trying to understand the max heap in python. Once I pop the element the elements are arranged as min heap.
...ANSWER
Answered 2022-Mar-15 at 07:33There is no special "property" to mark heap as max-heap.
Default in heapq is min-heap, all usual operations (like heappop) imply min-heap.
So you have to use underscored function versions again:
QUESTION
For example, given a List of Integer List list = Arrays.asList(5,4,5,2,2), how can I get a maxHeap from this List in O(n) time complexity?
The naive method:
...ANSWER
Answered 2021-Aug-28 at 15:09According to the java doc of PriorityQueue(PriorityQueue)
Creates a PriorityQueue containing the elements in the specified priority queue. This priority queue will be ordered according to the same ordering as the given priority queue.
So we can extend PriorityQueue as CustomComparatorPriorityQueue to hold the desired comparator and the Collection we need to heapify. Then call new PriorityQueue(PriorityQueue) with an instance of CustomComparatorPriorityQueue.
Below is tested to work in Java 15.
QUESTION
I have a class built using the pimpl idiom that represents a binary max Heap and it is not working properly: the program compiles and prints the content of the array but the array is not sorted correctly. In the examples I used in the main I should see the array sorted as: 100->19->36->17->3->25->1->2->7.
I checked multiple times the correctness of the heapify algorithm and I suspect that the problem lies in the constructor.
I'm looking for help to understand what is wrong with the code.
Regarding the way the pimpl idiom has been used, it comes from the first basic example explained in the book: "Effective Modern C++" of Scott Meyers. I know there are more efficient ways to use the pimpl idiom but that is not the purpose of this post.
...ANSWER
Answered 2022-Feb-19 at 18:17I should see the array sorted as: 10->19->36->17->3->25->1->2->7
That can't be, because in main() function you don't even put 25 in :-)
But anyway, here:
QUESTION
I have read about memory allocation for applications and I understand that, more or less, the heap, in memory, for a given application is dynamically allocated at the startup. However, there is also another concept called a min-heap, which is a data structure organized in the form of a tree where each parent node is smaller or equal to its children.
So, my question is: What are the relationships between the heap that is allocated at startup for a given application and the min-heap data structure that includes functions commonly referred to as 'heapify' and etc? Is there any relationship or is the min-heap data structure more of a higher level programming concept? If there is no relationship, is there any reason they've been given the same name?
This may seem like a silly question for some, but it has actually stirred up a debate at work.
...ANSWER
Answered 2022-Feb-17 at 01:38heap is a data structure which is actually a complete binary tree with some extra properties. There are 2 types of Heaps:
- MIN Heap
- MAX Heap
in min heap the root has the lowest value in the tree and when you pop out the root the next lowest element comes on the top. To convert a tree into heap we use heapify algorithm. It is also know as priority queue in c++. and usually as a competitive programmer we use STL function for heap so that we dont have to get into the hustle of creating a heap from scratch. Max heap is just the opposite with largest at the root. Usually heap is used because it has a O(logN) time complexity for removing and inserting elements and hence can even work with tight constraints like 10^6.
Now i can understand you confusion between heap in memory and heap data structure but they are completely different things. Heap in data structure is just a way to store the data.
QUESTION
I'm trying to figure out how I can initialize a min heap using an array. So far my function looks like this:
...ANSWER
Answered 2022-Feb-14 at 05:52Some remarks on the code you provided (not on the code you didn't provide):
arris a local variable, so whatever you do with it, once the function returns, thatarrwill be out of scope... and lost. You need an attribute or else subclasslistIt is not common practice to "allocate" the array and fill it with
None. In Python lists are dynamic, so you don't need to reserve slots ahead of time. You just need an empty list to start with.There is no need to call
heapifywhen the heap is empty.There is certainly no need to call
heapifymany times in a loop. All the logic for heapifying is already present in that method, so no need to call it on each index individually. But as stated in the previous point: no need to call it on an empty list -- there is nothing to move.
So the correction is quite basic:
QUESTION
Essentially I am looking for an efficient way to implement custom comparators using heapq.
For instance x = [('a',5),('c',3),('d',2),('e',1)]
I could heapify it heapq.heapify(x) then pop the min value heapq.heappop(x) which would return ('a', 5). How can I make it such that it returns in reverse lexicographical order ('e', 1)?
I know the convention when it comes to numbers is simply multiply the first element of the tuple by -1. Are there simple tricks like that when it comes to strings? I know I could potentially implement a map from a to z ... z to a but it sounds cumbersome.
ANSWER
Answered 2022-Jan-28 at 22:13For numbers you would do something like this:
QUESTION
I'm solving the Interviewbit code challenge Merge K Sorted Lists:
Merge k sorted linked lists and return it as one sorted list.
Example :
...
ANSWER
Answered 2022-Jan-22 at 15:52When I run your code locally with sample data, I get an error on:
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
Vulnerabilities
No vulnerabilities reported
Install heapify
Support
Reuse Trending Solutions
Find, review, and download reusable Libraries, Code Snippets, Cloud APIs from over 650 million Knowledge Items
Find more librariesStay Updated
Subscribe to our newsletter for trending solutions and developer bootcamps
Share this Page
