Python实现求一个集合所有子集的示例
方法一:回归实现
defPowerSetsRecursive(items): """Userecursivecalltoreturnallsubsetsofitems,includeemptyset""" iflen(items)==0: #ifthelsitisempty,returntheemptylist return[[]] subsets=[] first_elt=items[0]#firstelement rest_list=items[1:] #Strategy:Getallsubsetsofrest_list;foreachofthosesubsets,afullsubsetlist #willcontainboththeoriginalsubsetaswellasaversionofthesebsetthatcontainsthefirst_elt forpartial_sebsetinPowerSetsRecursive(rest_list): subsets.append(partial_sebset) next_subset=partial_sebset[:]+[first_elt] subsets.append(next_subset) returnsubsets
defPowerSetsRecursive2(items): #thepowersetoftheemptysethasoneelement,theemptyset result=[[]] forxinitems: result.extend([subset+[x]forsubsetinresult]) returnresult
方法二:二进制法
defPowerSetsBinary(items): #generateallcombinationofNitems N=len(items) #enumeratethe2**Npossiblecombinations foriinrange(2**N): combo=[] forjinrange(N): #testjthbitofintegeri if(i>>j)%2==1: combo.append(items[j]) yieldcombo
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