0
Q:

python priority queue

>>> import heapq
>>> heap = []
>>> heapq.heappush(heap, (5, 'write code'))
>>> heapq.heappush(heap, (7, 'release product'))
>>> heapq.heappush(heap, (1, 'write spec'))
>>> heapq.heappush(heap, (3, 'create tests'))
>>> heapq.heappop(heap)#pops smallest
(1, 'write spec')
>>> heapq.nlargest(2,heap)#displays n largest values without popping
[(7, 'release product'),(5, 'write code')]
>>> heapq.nsmallest(2,heap)#displays n smallest values without popping
[(3, 'create tests'),(5, 'write code')]
>>> heap = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
>>> heapq.heapify(heap)#converts a list to heap
>>> heap
[0, 1, 2, 6, 3, 5, 4, 7, 8, 9]
>>> def heapsort(iterable):
...     h = []
...     for value in iterable:
...         heappush(h, value)
...     return [heappop(h) for i in range(len(h))]
...
>>> heapsort([1, 3, 5, 7, 9, 2, 4, 6, 8, 0])
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
5
from queue import PriorityQueue

class PqElement(object):
    def __init__(self, value: int):
        self.val = value

    #Custom Compare Function (less than or equsal)
    def __lt__(self, other):
        """self < obj."""
        return self.val > other.val

    #Print each element function
    def __repr__(self):
        return f'PQE:{self.val}'

#Usage-
pq = PriorityQueue()
pq.put(PqElement(v))       #Add Item      - O(Log(n))
topValue = pq.get()        #Pop top item  - O(1)
topValue = pq.queue[0].val #Get top value - O(1)
0
import java.util.PriorityQueue;
import java.util.Iterator;

class Main {
    public static void main(String[] args) {

        // Creating a priority queue
        PriorityQueue<Integer> numbers = new PriorityQueue<>();
        numbers.add(4);
        numbers.add(2);
        numbers.add(1);
        System.out.print("PriorityQueue using iterator(): ");

        //Using the iterator() method
        Iterator<Integer> iterate = numbers.iterator();
        while(iterate.hasNext()) {
            System.out.print(iterate.next());
            System.out.print(", ");
        }
    }
}
1

New to Communities?

Join the community