Python 求最大子集的递归实现

def PowerSetsRecursive(items):  
    """Use recursive call to return all subsets of items, include empty set"""  

    if len(items) == 0:  
        #if the lsit is empty, return the empty list  
        return [[]]  

    subsets = []  
    first_elt = items[0] #first element  
    rest_list = items[1:]  

    #Strategy:Get all subsets of rest_list; for each of those subsets, a full subset list  
    #will contain both the original subset as well as a version of the sebset that contains the first_elt  

    for partial_sebset in PowerSetsRecursive(rest_list):  

        print('partial_sebset=',partial_sebset)
        subsets.append(partial_sebset)  
        next_subset = partial_sebset[:] +[first_elt]  
        subsets.append(next_subset)  
    return subsets  

#f=['a','b','c','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s']

f1=['a','b','c']

g=PowerSetsRecursive(f1)


print(g)

[[], ['a'], ['b'], ['b', 'a'], ['c'], ['c', 'a'], ['c', 'b'], ['c', 'b', 'a']]