Review the basics in 1 minute! Python Priority queue for fast minimums


Python has a convenient queue called heapq, which is used when you want to quickly retrieve the minimum value from a list, so let's review it quickly. Frequent content even in AtCoder

For those in a hurry

All of this article. Third line q = heapq.heapify(a) Be careful because it does not move

a = [1,2,3,4,6,7,8]
#Heapify list with heapify.

#Add 5 with heappush.

#The elements in the heap are extracted by heapop in ascending order.
while a:
######Execution result######

Simple explanation

・ Heap **. Heapify (list) ** If you give a list, it will be heaped

・ Heap. ** heap push (heap, element) ** Add a new element to heap (heap version of append in list)

・ Heap. ** heapop (heap) ** Get the smallest value in the heap. The retrieved element is deleted from the heap.


I want to create a priority queue that retrieves the maximum value

** All values ​​can be signed in reverse. ** **

a = [1,2,3,4,6,7,8]

#Reverse the sign of the element
for i in range(len(a)):
  a[i] = a[i]*(-1)

while a:
  #I will return the sign of the output

######Execution result######


Referenced site

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