2822两种思路c++

思路1 从第一项开始

#include <iostream>

#include <iomanip>

using namespace std;

int main() {

int fz = 2, fm = 1, n;

cin >> n;

double  sum = 0;

for (int i = 1; i <= n; i++) {

sum += 1.0 * fz / fm;

int c = fz + fm;

fm = fz;

fz = c;

}

cout << fixed << setprecision(4) << sum << endl;

return 0;

}

思路2