SCIP in C++11 ― 2.2.2節 その4

冪集合：問題2.32

ここもlistやtupleではえらい苦労した部分。

今やすっきり。

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typedef List Set;

typedef List SetList;

const SetList subsets(const Set& s)

{

    if(isNull(s)){return(makeList(makeList()));}

    const SetList rest(subsets(cdr(s)));

    const function<SetList(Set)> addCar2SetList=

        [s](const Set& x){return(cons(car(s),x));};

    return(append(rest,mapping(addCar2SetList,rest)));

}

int main(int argc, char** argv)

{

    const auto list1(makeList(1,2,3));

    cout<<"x = "<<listString(list1)<<endl;

    const auto subsetList(subsets(list1));

    cout<<"2^x = "<<listString(subsetList)<<endl;

    return(0);

}

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出力

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x = (1 2 3)

2^x = (() (3) (2) (2 3) (1) (1 3) (1 2) (1 2 3))