python中的列表检查小算法问题

Question

我想做一个小程序，得到满足'x+y = sum‘的列表中的所有夫妇(x，y)

ar= [1,2,3,4,5,3,6,7,9,8,10,13,18]

sum = 9


for i in ar:

    noclubs = [x for x in ar if x != ar[i]]
    for z in noclubs:
        if ar[i] + noclubs[z] == sum:
            print(ar[i],noclubs[z])

它向我显示了这个错误“如果ari + noclubsz == sum: IndexError: list index超出范围”

这是代码，请帮我

Answer 1

您可以使用迭代变量代替。

ar= [1,2,3,4,5,3,6,7,9,8,10,13,18]

sum = 9


for i in ar:

    noclubs = [x for x in ar if x != i]
    for z in noclubs:
        if i + z == sum:
            print(i,z)

Answer 2

代码更多，但可能更有效率。这是因为如果列表中的任何元素大于或等于目标值，那么在计算中包含它或更高的元素是没有意义的。所以：

from itertools import combinations

ar = [1,1,2,3,4,5,3,6,7,9,8,10,13,18]

total = 9

def get_pairs(a, s):
    result = set()
    for combo in combinations([e for e in a if e < s], 2):
        if sum(combo) == s:
            result.add(combo)
    return result

print(get_pairs(ar, total))

输出：

{(4, 5), (1, 8), (2, 7), (3, 6)}