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]
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)
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(", ");
}
}
}