Created
April 8, 2013 11:41
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求某个集合的所有子集
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#-*- coding: utf-8 -*- | |
""" | |
给定集合 test_case | |
输出其所有子集 | |
""" | |
def getsubs(father, size): | |
"""获取集合 father 的 | |
指定长度 size 的所有子集合""" | |
all_subs = [] | |
excludes = set() | |
for i in father: | |
sub = set() | |
sub.add(i) | |
if len(sub) == size: | |
all_subs.append(sub) | |
else: | |
excludes.add(i) | |
new_father = father.difference(excludes) | |
_sub = getsubs(new_father, size-1) | |
for s in _sub: | |
all_subs.append(sub.union(s)) | |
return all_subs | |
test_case = set((1,2,3,4)) | |
test_len = len(test_case) | |
subsets = [] | |
test_case_copy = test_case.copy() | |
for size in range(1, test_len): | |
# 用内置的 itertools.combinations 更方便 | |
subs = getsubs(test_case_copy, size) | |
subsets.extend(subs) | |
# 添加空集和集合本身 | |
subsets.append(set()) | |
subsets.append(test_case) | |
print subsets |
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