利用vector定义数组大小，static_cast显式转换

解题思路:

注意事项:

参考代码:

#include <iostream>

using namespace std;

#include <vector>

int main()

{

int n = 0;

cin >> n;

switch(n)

{

case 1:

{

cout << "2.00" << endl;

break;

}

case 2:

{

cout << "3.50" << endl;

break;

}

default:

float s = 3.50f;

vector<int> arr1(n), arr2(n);//需包含头文件vector

arr1[0] = 2;

arr1[1] = 3;

arr2[0] = 1;

arr2[1] = 2;

for (int i = 2; i < n; ++i)

{

arr1[i] = arr1[i - 1] + arr1[i - 2];

arr2[i] = arr2[i - 1] + arr2[i - 2];

s += (static_cast<float>(arr1[i]) / static_cast<float>(arr2[i]));//显式转换

}

printf("%.2f", s);

}

return 0;

}