我正在嘗試在 Python 中使用 PriorityQueue 構(gòu)建優(yōu)先級隊(duì)列，但不是要考慮進(jìn)行優(yōu)先級比較的元素，而是希望它在將元素傳遞給函數(shù)后使用函數(shù)的返回值，類似于 sorted(mtlist,key = myfun），有沒有辦法做到這一點(diǎn)，
3 回答
尚方寶劍之說
TA貢獻(xiàn)1788條經(jīng)驗(yàn) 獲得超4個(gè)贊
與其將元素直接插入隊(duì)列，不如將每個(gè)元素包裝在一個(gè)元組中，其中元組中的第一個(gè)元素是所需的排序鍵。元組按其元素的順序排序（即，首先比較第一個(gè)元素），因此排序鍵需要排在第一位。
import heapq
queue = []
my_list = [...]
for element in my_list:
heapq.heappush(queue, (my_func(element), element))
慕的地8271018
TA貢獻(xiàn)1796條經(jīng)驗(yàn) 獲得超4個(gè)贊
如果您有元素的包裝類，那么您可以使用運(yùn)算符重載。
例如，假設(shè)您有一個(gè)CustomNumber類（相當(dāng)于您的元素），其中順序由模 16 值（私有函數(shù)__f()）確定，您可以覆蓋比較運(yùn)算符，例如：
class CustomNumber:
def __init__(self, value):
self.value = value
def __f(self, x):
return x % 16
def __lt__(self, obj):
"""self < obj."""
return self.__f(self.value) < self.__f(obj.value)
def __le__(self, obj):
"""self <= obj."""
return self.__f(self.value) <= self.__f(obj.value)
def __eq__(self, obj):
"""self == obj."""
return self.__f(self.value) == self.__f(obj.value)
def __ne__(self, obj):
"""self != obj."""
return self.__f(self.value) != self.__f(obj.value)
def __gt__(self, obj):
"""self > obj."""
return self.__f(self.value) > self.__f(obj.value)
def __ge__(self, obj):
"""self >= obj."""
return self.__f(self.value) >= self.__f(obj.value)
這樣下面的代碼：
a = CustomNumber(16)
b = CustomNumber(14)
print('a < b =', a < b)
print('a <= b =', a <= b)
print('a == b =', a == b)
print('a != b =', a != b)
print('a > b =', a > b)
print('a >= b =', a >= b)
印刷：
a < b = True
a <= b = True
a == b = False
a != b = True
a > b = False
a >= b = False
12345678_0001
TA貢獻(xiàn)1802條經(jīng)驗(yàn) 獲得超5個(gè)贊
Here is an example of using custom sort in PriorityQueue in Python.
We use a priority-queue (heapq) find the next element to add. To make the
implementation simple we "monkey patch" the ListNode class to have a custom
less-than function using setattr. Note that, simply using the tuple trick
and pushing (node.val, node) to the priority queue will not work because
the lists have values in common.
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
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