heapq 自定义对象

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/baidu_27643275/article/details/88878612

heapq +__lt__

自定义对象结构，并重载__lt__操作符

import heapq
class MyObject:
    def __init__(self, val):
        self.val = val

    def __lt__(self, other):
        return self.val > other.val
q = []
heapq.heappush(q, MyObject(50))
heapq.heappush(q, MyObject(40))
heapq.heappush(q, MyObject(30))
heapq.heappush(q, MyObject(20))
heapq.heappush(q, MyObject(200))
obj = heapq.heappop(q)
print(obj.val)

heapq+lambda

https://stackoverflow.com/questions/8875706/heapq-with-custom-compare-predicate

heapq模块可以接受元组对象，默认按照元组的第一个元素构成小根堆

heappush( Q , tuple )

如果想要按照元组中的其他元素构成小根堆，可以通过以下方式进行，在原来基础上加个优先级即可：

heappush( Q , ( priority, tuple ) ) 优先级取负则构成一个大根堆
priority = key(tuple[i])
key=lambda x:x

import heapq
from heapq import *

def FindMaxProfit(costs, profits, key=lambda x: x):
    maxHeap = []
    for i in range(len(costs)):
        heappush(maxHeap, (-key(profits[i]), costs[i], profits[i]))
    return heappop(maxHeap)[2]

# for test
costs = [5, 10, 60, 20]
profits = [3, 2, 4, 9]
print(FindMaxProfit(costs, profits))  # 9

应用

项目收益问题