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Questions tagged [heapq]

A Python module that implements the heap queue algorithm. Use only when the question is specific to this heap implementation, as opposed to heap mechanics in general.

Module documentation: heapq

Alternative, using a different interface: queue.PriorityQueue

See also the language-agnostic tag.

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Python, heapq: difference between heappushpop() and peeking/popping

Is there a significant difference in functionality and/or efficiency between using heappushpop and peeking at the heap first then deciding whether to pop (using heapreplace)? E.g. from heapq import * a = [5, 18, 9, 14, 22] heapify(a) # a = [5, 14,…
g999
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numba jit mode memory leak issue?

I am currently facing a weird memory leak problem when having jit decorator on a function which uses heapify takings results from another jitted function which return results in yield style here is the idea of the design to indicate the…
Axd
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Why do I get TypeError, when trying to find the max element of a heap with function 'nlargest'?

I was trying to find the maximum element of a heap and found a function heapq.nlargest to use. Then got this error at the line commented below: TypeError at line 10: 'NoneType' object is not iterable. So here is the code: from heapq import * from…
Alexey Dulin
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Unorderable type error while pushing into heap

I have a list of heads of N Linked Lists which I am trying to merge based on their value using heaps. Since heapq works with first value in tuples for sorting in heap I wrote the following code: def mergeKLists(self, A): # A contains list of Linked…
Abhishek Agarwal
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Why does the Python heapq _siftup(...) call _siftdown(...) at the end?

The code for_siftup at github - python/cpython/Lib/heapq.py has a final call to _siftdown: def _siftup(heap, pos): endpos = len(heap) startpos = pos newitem = heap[pos] # Bubble up the smaller child until hitting a leaf. …
aksg87
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Interviewbit - Merge k sorted linked lists: heappop returns max element instead of min

I'm solving the Interviewbit code challenge Merge K Sorted Lists: Merge k sorted linked lists and return it as one sorted list. Example : 1 -> 10 -> 20 4 -> 11 -> 13 3 -> 8 -> 9 will result in 1 -> 3 -> 4 -> 8 -> 9 -> 10 -> 11 -> 13 -> 20 The…
K2G
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Sorting (or partially sorting) a list of objects based on a specific attribute

Problem I have a list of objects. Each object has two attributes: "score" and "coordinates". I need to find the largest N objects of the list based on the score attribute. The main problem I'm having is sorting the objects using only the score…
spengler
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Understand dict.get without braces in Python

For the question https://leetcode.com/problems/top-k-frequent-elements to find top k frequent elements I understand we can use heapq.nlargest() method but for that the key used is just dict.get without braces -…
user17267565
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Weird Python heap: heappop() output at the first time

the first heappop() is not the min of array, while it's the first index. After that, heappop() works I thought maybe it's the automatic heapify() after heappop()? check the documents but find nothing >>> a =…
Cici Hou
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Merging k sorted lists using heapq module in python3

Problem:- merge k sorted lists. I want to solve this problem using min heap which can be implemented with heapq module in python. Below is the sample code of the function... heapq.heappush(listwithoutNone,(node.val, node)) But the problem…
Abhishek Jaiswal
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Why PyCharm debugger crashes with "ImportError: cannot import name 'heappush'"

I have a project in PyCharm that its debugger began crashing after I added a few lines of code. I deleted all the code and left a simple print in the file. The code is located in the folder: "heapq\test_heapq.py" as shown in screenshot 1. The error…
RaamEE
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Listing the shortest path available using heapq for dijkstra shortest path algorithm

I was given a task where I need to apply Dijkstra's Shortest Path Algorithm in my python code. Let say we have a few cities involved. I need to find the one that has the shortest route. In summary, the task is to: Find the shortest route. List all…
Muhammad Zahirul Iman
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heap time complexity python

import heapq def getMaxUnit(num,boxes,UnitSize,UnitSize,unitPerBox, truckSize): if truckSize == 0 or num == 0: return 0 h = [] for i in range(num): h.append((-1*unitPerBox[i],boxes[i])) heapq.heapify(h) …
CodeEnthusiast
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Applying Dijkstra with heapq: 'generator' object is not subscriptable

As the title suggests i'm trying to apply dijkstra algorithm with a Heapq (following bogotobogo.com on dijksta in python with slight modifications - long link;could't type), and i'm getting TypeError: 'generator' object is not subscriptable with the…
Mohab Khaled
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How to use heapq module

I don't understand how I can properly use heapq module. I realized that without transforming my list to a heap (without using heapify) I can still use other functions which require a heap as input (heappop, heappush..). So when do I need to use…
kneazle
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