假设n>如何从n个数字的列表中找到k个最大数字. ķ [英] How to find k biggest numbers from a list of n numbers assuming n > k

问题描述

我正在寻找Python中的某些代码，这些代码可以从n个数字的未排序列表中返回最大k个数字.首先，我想通过首先对列表进行排序来做到这一点，但这可能会变得非常庞大.

I am looking for some code in Python which could return k largest numbers from an unsorted list of n numbers. First I thought to do this by sorting the list first, but this might turn out to be very bulky.

例如，我要从中查找最大数字k的列表是list1

For example the list from which I want to find k largest number be list1

> list1 = [0.5, 0.7, 0.3, 0.3, 0.3, 0.4, 0.5]

在n = 7处，如果是k = 3，即我要从7个数字的列表中找到3个最大的数字，则输出应为0.5, 0.7, 0.5

Here n = 7 and if k = 3, that is if I want to find 3 largest numbers from a list of 7 numbers then output should be 0.5, 0.7, 0.5

这怎么办?

推荐答案

Python包含所有电池-使用

Python has all batteries included - use heapq module :)

from heapq import nlargest

data = [0.5, 0.7, 0.3, 0.3, 0.3, 0.4, 0.5]
print nlargest(3, data)

比使用整个堆排序还快，因为它使用了部分堆排序

it's also faster than sorting the whole array, because it's using partial heapsort

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