在整数列表中查找所有加起来为数字的数字 [英] Find all numbers in a integer list that add up to a number

问题描述

面试中有人问我这个问题.给出以下列表:

I was asked this question on an interview. Given the following list:

[1,2,5,7,3,10,13]

找到加起来为5的数字.

Find the numbers that add up to 5.

我的解决方法如下:

#sort the list:
l.sort()
result = ()
for i in range(len(l)):
    for j in range(i, len(l)):
         if l[i] + l[j] > 5:
             break
         elif l[i] + l[j] == 5:
             result += (l[i], l[j])

我提出的想法是对列表进行排序，然后循环查看总和是否大于5.如果是，那么我可以停止循环.我感觉到面试官对这个答案不满意.有人可以提出更好的建议供我将来参考吗?

The idea I presented was to sort the list, then loop and see if the sum is greater than 5. If so, then I can stop the loop. I got the sense the interviewer was dissatisfied with this answer. Can someone suggest a better one for my future reference?

推荐答案

这将返回输入功率集的所有元素，这些元素的总和为5:

This will return all elements of the powerset of the input that sum up to 5:

>>> input = [1,2,5,7,3,10,13]
>>> import itertools
>>> def powerset(l):
...     return itertools.chain.from_iterable((itertools.combinations(l, i) for i in range(len(l)+1)))
...
>>> filter(lambda v: sum(v) == 5, powerset(input))
[(5,), (2, 3)]

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