有一分数序列： 2/1 3/2 5/3 8/5 13/8 21/13...... 求出这个数列的前N项之和，保留两位小数。

解题思路:

注意事项:

参考代码:

#include<iostream>

using namespace std;

#include<iomanip>

float seqSum(short n);

int main()

{

short N = 0;

cin >> N;

cout << fixed << setprecision(2) << seqSum(N) << endl;

}

float seqSum(short n)

{

float sum = 0;

short fenzi = 2;

short fenmu = 1;

for (short i = 0; i < n; i++)

{

sum += (float)fenzi / fenmu;

short linshifenmu = fenmu;

fenmu = fenzi;

fenzi += linshifenmu;

}

return sum;

}