# Questions tagged [priority-queues]

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### Can you simulate the following process in $O(N.log N)$

Given an array $A[]$ of N integers. pseudocode: Traverse from left to right of this array. Let's say you are standing at index $j$. For each index i=1 to i=j-1, increment all $A[i]$ by $1$ if and ...
1 vote
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### How can we prove that "extract almost minimum" operation in a priority queue cannot be done in o(log n)?

Suppose we want to create a priority queue with 2 operations: insert and extract almost min. Extract almost min operation selects either the first minimum or a second minimum item from the structure ...
87 views

### Looking for name of a priority queue data structure based on bit-boundary buckets

(Note: cross-listed on stack overflow: https://stackoverflow.com/questions/73362856/looking-for-name-of-a-priority-queue-data-structure-based-on-bit-boundary-bucket) I'm looking for the name of a data ...
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### Does order of elements in a set matter in Dijkstra's Algorithm?

When we use a set for doing Dijkstra's Algorithm, we use a pair of {distance,node} which we insert in a set. Most of the articles say that the first element of pair should be the distance , else we ...
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### Did I invent a new data structure?

I needed to implement a priority queue for a project I'm working on and had this idea. In a priority queue BST implementation wouldn't it be more efficient if the poll node pointed to its parent since ...
1 vote
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### Monotone priority queues

I'm a little confused about how monotone priority queues work. As far as I understand: A queue is a FIFO data structure A priority queue is a queue where the current element of highest (or lowest) ...
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### Implementing an efficent priority queue using only stacks

Is it possible to implement an efficient priority queue (as efficient as a heap) only using the stack data structure? The usual efficiency for a priority queue which is implemented using a heap is : ...
1 vote
354 views

### Priority Queue Using Stack

Can one build a priority queue using stacks, such that the priority queue has the same complexity for each operation. Could it be done? If so how? If not what is the best solution that can be done? ...
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1 vote
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### Numerical Accuracy & Sorting Algorithms?

Sedgewick and Wayne talk about how sorting algorithms and, specifically, priority queues are used in devising ways to improve accuracy in floating-point calculations: https://algs4.cs.princeton.edu/...
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1 vote
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### How to compute the general term formula for the number of full binary tree heaps that can be formed with distinct elements?

The number of possible heaps that are full binary trees of height $h$ and can be formed with ($n = 2^h - 1$) distinct elements can be computed by recursion:  a_h = {2^h - 2 \choose 2^{h - 1} - 1} a_{...
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### Dijkstra without decrease key

I was reading through this paper, "Priority Queues and Dijkstra's Algorithm" by Mo Chen et al., which suggests using Dijkstra's without edge relaxation, but to rather to just insert new ...
• 153
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### Making an array increasing by modifying elements

I am trying to solve a problem on codeforces. Given an integer array $a_1,\ldots,a_n$, our goal is to find the minimal number of instructions, each of which increments or decrements a single entry, ...
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### Why can't we replace Dijkstra's priority queue with a regular queue?

I am confused why we can't simply use a normal queue instead of a priority queue for Dijkstra's. I agree that you can find the shortest path in fewer iterations of the while loop using a priority ...
54 views

### Parallelization of priority queue-based algorithms

There's a number of algorithms that operate by maintaining and consuming a priority queue of "events". I'm thinking primarily of geometric algorithms, particularly sweep-line algorithms like Bentley-...
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### When inserting an element in a priority queue and the heap size is already at max capacity, should you output an error OR increase the array size?

I'm currently learning about how to implement priority queues using heaps, but I've hit a wall while trying to implement the insertion operation. Assume that the size of the array storing the ...
1 vote
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### Priority queue with a buffer for delayed insertion and other tweaks

I was thinking of ways to optimise a (heap-based) priority queue in certain scenarios, like in best-first path search algorithms (Dijkstra, A*, etc.). One possible optimisation is to delay insertions ...
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### Short Fibonacci Heap

Is it possible to create a Fibonacci Heap that has exactly 5 nodes: one root node and 4 children of that root?. If yes please explain the sequence of operations to do so. If it is not possible then ...
1 vote
115 views

### An algorithm to drop low-priority items from a heap-based priority queue

I am looking for an efficient algorithm to drop from a complete binary min heap all items whose weight exceeds a given value. (Or, equivalently, to drop from a priority queue realised by such a heap ...
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### Merging balls interview problem

Here is an interview problem about balls rolling towards buckets from Sprinklr Interview Experience at GeekforGeeks. You are given $n$ balls on the table and all the balls are rolling towards the ...
1 vote
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### Heap operating in time $\Gamma^{-1}(n)^2$

I have a priority queue implementation which I claim has the following worst case asymptotic run-times for the given operations: PEEK_MIN …………………………… O(1) POP_MIN…………………………… O( (INVERSE_Γ(n)) ^2). ...
1 vote
552 views

### Is there a name for this priority queue data structure?

While watching a sports tournament, I noticed that the tournament tree looks a lot like a heap. I came up with the following data structure: A complete binary tree where the leaves are elements of ...
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### Why is a heap better than a linked list for implementation of a priority queue?

Using a heap, you have O(log(n)) insertion and O(log(n)) removal. Using a linked list, you have O(n) insertion and O(1) removal. Why is it better to have log-n for both than n for one and constant ...
1 vote
131 views

### How priority queue is used in Dijsktra algorithm?

I have difficulties understanding how the priority queue is used in Dijkstra algorithm. Wikipedia lists 3 operations performed on priority queue: add_with_priority(), extract_min(), ...
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1 vote
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### Sorting in a Priority Queue

Does a priority queue Queue<K,V> always sort its elements based on the value of each element or its key? I know than the priority in the queue is based on ...
1 vote
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### Complexity of closest set of points in plane problem

Given a set of points on a plane find the set of $n$ points that are closest to the origin. (Points are pairs of integers.) Input: list of points. Initialize a priority queue $Q$, where ...
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1 vote
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### Priority queue of constant size fit for extraction of K highest priority elements

In an algorithm I'm designing, I need to do this cycle on a priority queue of constant size N many times, as quickly as possible: get $K$ highest priority elements (do on them some outside ...
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### How would a priority queue be implemented in a functional programming language?

How would a priority queue be coded efficiently in a functional programming language? I'm new to functional programming, but I'm having difficulty understanding how a data structure that seems to ...
1 vote
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### Correct term for a priority queue with unique elements

Is there a standard term for a priority queue which can only hold a single occurrence of any element? This would be a priority queue for which operations such as "raise the priority of element ...
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1 vote
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### Leftist Tree initialization in O(n) time

In the book Handbook of Data Structures and Applications, section 5.2.5, (copy of the relevant section available here) about leftist queues, the author(s) state the following: For the complexity ...
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### Find K largest elements using a priority queue [duplicate]

Say we have a Priority Queue of size 1000 that is implemented using Max Heap. Now if i want to get the top 5 elements, the most laid back method is to poll the maximum 5 times, resulting in a set of ...
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