通过常量表达式或模板函数在编译时获取多维std::array的大小

#include <array>
#include <iostream>

int main() {
    std::array<std::array<int, 3>, 4> arr;

    constexpr int rows = arr.size();
    constexpr int cols = arr[0].size();

    std::cout << "Number of rows: " << rows << std::endl;
    std::cout << "Number of columns: " << cols << std::endl;

    return 0;
}

#include <array>
#include <iostream>

template <typename T, std::size_t N>
constexpr std::size_t getArraySize(const std::array<T, N>& arr) {
    return N;
}

template <typename T, std::size_t N, std::size_t M>
constexpr std::size_t getArraySize(const std::array<std::array<T, M>, N>& arr) {
    return N * getArraySize(arr[0]);
}

int main() {
    std::array<std::array<int, 3>, 4> arr;

    constexpr std::size_t rows = getArraySize(arr);
    constexpr std::size_t cols = getArraySize(arr[0]);

    std::cout << "Number of rows: " << rows << std::endl;
    std::cout << "Number of columns: " << cols << std::endl;

    return 0;
}