如何用尾递归求解n/2n+1数列的和

Question

1/3+2/5+4/9+……+n/2n+1的和

Answer 1

注意题目要求是尾递归

#include <iostream>

double sum(int n, double s = 0.0)
{
    if (n == 0)
        return s;
    else
        return sum(n - 1, s + static_cast<double>(n) / (2 * static_cast<double>(n) + 1));
}

int main()
{
    int n;
    std::cin >> n;
    if (n < 0) {
        std::cerr << "requires n >= 0" << std::endl;
        return -1;
    }
    std::cout << sum(n) << std::endl;
    return 0;
}