如何在不使用Itertools的情况下找到列表元素的所有组合

Question

我正在寻找一种算法，该算法可以找到列表元素的所有可能组合，而无需使用itertools。例如。：对于[1,2,3,4,5]，它打印[[1]，[2]，[3]，[4]，[5]，[1,2]，[1,3]，[1，4]，[1,5]，[2,1] ........]

Answer 1

使用递归提供了一个解决方案。

>>> import copy
>>> def combinations(target,data):
...     for i in range(len(data)):
...         new_target = copy.copy(target)
...         new_data = copy.copy(data)
...         new_target.append(data[i])
...         new_data = data[i+1:]
...         print new_target
...         combinations(new_target,
...                      new_data)
...                      
... 
>>> target = []
>>> data = ['a','b','c','d']
>>> 
>>> combinations(target,data)
['a']
['a', 'b']
['a', 'b', 'c']
['a', 'b', 'c', 'd']
['a', 'b', 'd']
['a', 'c']
['a', 'c', 'd']
['a', 'd']
['b']
['b', 'c']
['b', 'c', 'd']
['b', 'd']
['c']
['c', 'd']
['d']