Question

请教一道c语言的题?

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

Answer 1

int cnt = 20;/*20次，改成其他亦可*/
int a=2, b=1;
float sum = 0.0;

while(cnt-->0)
{
sum+=((float)a/b);
a+=b;
b=a-b;/*即是原来的a*/
}

printf("%f",sum);

Answer 2

绝对正确的解答：
#include<conio.h>
#include<stdio.h>
fun(int n)
{int a,b,c,d,k;double s;
s=0.0;a=2;b=1;
for(k=1;k<=n;k++)
{
s=s+(double)a/b;
c=a;a=a+b;b=c;
}
return s;
}
main()
{int n=5;
clrscr();
printf("\nThe value of function is: %lf\n",fun(n));
}

Answer 3

/*FABONACCI数列分式运算*/
main()
{
float a, b, c, d, e, f,sum=0;
int i,n;
n=20；

a = 2;b = 1;
c = 3;d = 2;
sum = a / b + c / d;
e = a + c;
f = b + d;
for(i=2;i<n;i++)
{
sum = sum + e / f;
e = e + c;
f = f + d;
c = e;
d = f;
}
printf("%f",sum);
getch();
}