Problem2-Project Euler

Even Fibonacci numbers

 

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

找出400 0000以下斐波那契数中的偶数求和，累加即可（用递推公式，通项公式可能有舍入误差）

 #include"stdio.h"

 int main()        /*problem2-Even Fibonacci numbers*/
 {
     int a[]={,,},i;
     double sum=;
     for(i=;;i++)
     {
         a[i]=a[i-]+a[i-];
         if(a[i]>4000000.0||i==)
             break;
     }
     for(i=;a[i]!=;i+=)
         sum+=a[i];
     printf("sum is %lf\n",sum);
     return();
 }