C++语言：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20项之和

Question

#include <iostream>
using namespace std;
int main()
{
int n;
double a, b,sum,tem;
while ( n = 1, n <= 20, n++)
{
sum += b / a;
tem = b;
b = a + b;
a = tem;
}
cout << "sum" << sum << endl;

return 0;
}
我这样做怎么没有值输出的？

Answer 1

while ( n = 1, n <= 20, n++)

应该是 for( n = 1; n <= 20; n++)

追问

C++中while也是循环语句啊，而且我用for( n = 1; n <= 20; n++)也是不行的。不知道是不是我建的项目有问题，还是电脑有问题了？

追答

用while就这么写
int n = 20;
while ( n > 0)
{
sum += b / a;
tem = b;
b = a + b;
a = tem;
n--;
}