将 int 数组转换为 std::vector<int*>

Question

I'm trying to "convert" an integer C style array to std::vector<int*> without using a for loop, or rather insert pointers of all array items in a vector.

I'm currently implementing this by doing the follow:

for (size_t i = 0; i < 5; i++)
{
    vector.push_back(&values[i]);
}

Is it possible to implement this by using std::vector::insert() and std::being/end ?

Answer 1

std::transform is a useful algorithm in <algorithm> for copying values between containers that aren't implicitly compatible but for which you can provide a transformation function.

Here is an example of how you could populate a std::vector<int*> from a std::array<int, N>

int values[5] = { 1,2,3,4,5 };
std::vector<int*> v1;

std::transform(
    std::begin(values), std::end(values),   // Copy from
    std::back_inserter(v1),                 // Copy to
    [](auto& i) {                           // Transformation function
        return &i;
    });

Edit : Changed std::array<int, 5> to int[5] to account for edits in the question.

Answer 2

The code below is rather fancy way to do what you want, but it is generic and it doesn't use for loop - it just passes pointers of array's elements to vector constructor:

template<class T, size_t ... Ints, size_t N>
std::vector<T*> makePtrsHelper(std::array<T,N>& arr, std::index_sequence<Ints...>) {
       return std::vector<T*>{ & std::get<Ints>(arr)... }; 
       // vector ctor taking pointers to array's elements
}

template<class T, size_t N>
std::vector<T*> makePtrs(std::array<T,N>& array) {
    return makePtrsHelper(array, std::make_index_sequence<N>{});
}

int main(){
    std::array<int,5> ar{1,2,3,4,5};
    std::vector<int*> v = makePtrs(ar);

Live demo

Answer 3

Note : as pointed out in comments my below answer is wrongly related to vector<int> not vector<int*> which was asked for in question.

---

Solution with std::copy and C-style array:

int ar[] = {1,2,3,4,3,2,1};
std::vector<int> vec;
std::copy(ar, ar+sizeof(ar)/sizeof(ar[0]), back_inserter(vec));