Even Fibonacci numbers

problem 2：Even Fibonacci numbers

题意：求斐波那契数列不大于4百万的值为偶数的和

代码如下：

 1 #ifndef PRO2_H_INCLUDED
 2 #define PRO2_H_INCLUDED
 3 #include<iostream>
 4 using namespace std;
 5
 6 namespace pro2{
 7     int solve(){
 8         int p1=1,p2=2,p,sum=0;
 9         for(;p1<=4000000;){
10             if(p1%2==0)sum+=p1;
11             p=p1+p2;
12             p1=p2;
13             p2=p;
14         }
15         return sum;
16     }
17 }
18
19 #endif // PRO2_H_INCLUDED