Even Fibonacci Numbers Problem & Solution
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.
See the even Fibonacci numbers problem on Project Euler.
C++ Solution
#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")
#include <iostream>
using namespace std;
static const int _=[](){ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
int main() {
int sum = 0;
int first = 1;
int second = 2;
while (second < 4000000) {
if (second % 2 == 0) {
sum += second;
}
int tmp = first + second;
first = second;
second = tmp;
}
cout << sum << endl;
}