Read the problem statement here:

Project Euler: https://projecteuler.net/problem=2

HackerRank: https://www.hackerrank.com/contests/projecteuler/challenges/euler002/problem

Java code:

import java.util.*; class Solution{ public static void main(String[] args){ Scanner in = new Scanner(System.in); int t = in.nextInt(); while(t– > 0){ long n = in.nextLong(); System.out.println(SumEvenFibo(n)); } in.close(); } static long SumEvenFibo(long n){ long first = 1, second = 2, next = 3, sum = 2;

```
while(second < n){
if(next % 2 == 0){
sum += next;
}
next = first + second;
first = second;
second = next;
}
return sum;
}
```

}

It has a \(O(n)\) time complexity.

This problem can be solved in \(O(1)\) time. Read the post here.