^ython heap code example

Example 1: heapq python how to use comparator

class Solution:
    def mergeKLists(self, lists: List[ListNode]) -> ListNode:
        
        setattr(ListNode, "__lt__", lambda self, other: self.val <= other.val)
            
        pq = []
        for l in lists:
            if l:
                heapq.heappush(pq,  l)
        
        out = ListNode(None)
        head = out
        while pq:
            l = heapq.heappop(pq)
            head.next = l
            head = head.next
            if l and l.next:
                heapq.heappush( pq, l.next)
            
        return out.next

Example 2: python heapq

>>> 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]