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列出集合的所有子集的numpy实现
source link: https://allenwind.github.io/blog/10997/
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Mr.Feng Blog
NLP、深度学习、机器学习、Python、Go
列出集合的所有子集的numpy实现
纯numpy实现的非递归方法。
考虑到集合中每个元素在子集中有两种状态，分别为存在与不存在，因此总共有2n2n种可能，每种可能0,1,2,…,2n−10,1,2,…,2n−1都可以用二进制表示，例如n=10n=10时（元素个数，也是二进制的宽度），二进制表示为0001100100。因此获得对应关系，0表示元素不会出现在子集中，1表示出现在子集中。
利用这种对应关系，使用numpy的编程实现，
import numpy as np
def list_all_sub_groups(es):
n = len(es)
for i in range(2 ** n):
idx = (np.array(list(np.binary_repr(i, n))) == "1")
yield es[idx]
es = np.array(["a", "b", "c", "e", "f"])
for e in list_all_sub_groups(es):
print(e)
结果如下，
[]
['f']
['e']
['e' 'f']
['c']
['c' 'f']
['c' 'e']
['c' 'e' 'f']
['b']
['b' 'f']
['b' 'e']
['b' 'e' 'f']
['b' 'c']
['b' 'c' 'f']
['b' 'c' 'e']
['b' 'c' 'e' 'f']
['a']
['a' 'f']
['a' 'e']
['a' 'e' 'f']
['a' 'c']
['a' 'c' 'f']
['a' 'c' 'e']
['a' 'c' 'e' 'f']
['a' 'b']
['a' 'b' 'f']
['a' 'b' 'e']
['a' 'b' 'e' 'f']
['a' 'b' 'c']
['a' 'b' 'c' 'f']
['a' 'b' 'c' 'e']
['a' 'b' 'c' 'e' 'f']
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