# CPP Program for Even Fibonacci Numbers with Source Code

## Problem:

• 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.

## Algorithm:

• As explained in the problem statement, you can compute all Fibonacci numbers in an iterative way:
• `F_i=F_{i-2}+F_{i-1}`
• My variables ”a” and ”b” stand for `F_{i-2}` and `F_{i-1}` whereas ”next” is `F_i`
• After each iteration, ”next=a+b” and then ”a” becomes ”b” and ”b” becomes ”next”.
• A number is even if there is no remainder when divided by 2.
• In most programming languages it’s written as ”variable % 2 == 0”
• Internally, your compiler might translate this to the more efficient ”(variable & 1) == 0”

## Note:

• ”unsigned long long” is required to pass all Hackerrank tests.

## Program:

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```#include <iostream>

int main()
{
unsigned int tests;
std::cin >> tests;
while (tests--)
{
unsigned long long last;
std::cin >> last;

unsigned long long sum = 0;
// first Fibonacci numbers
unsigned long long a = 1;
unsigned long long b = 2;

// until we reach the limit
while (b <= last)
{
// even ?
if (b % 2 == 0)
sum += b;

// next Fibonacci number
auto next = a + b;
a = b;
b = next;
}

std::cout << sum << std::endl;
}
return 0;
}
```Code language: C++ (cpp)```