104 lines
2.0 KiB
Markdown
104 lines
2.0 KiB
Markdown
---
|
|
id: 5900f36e1000cf542c50fe81
|
|
title: 'Problem 2: Even Fibonacci Numbers'
|
|
challengeType: 5
|
|
forumTopicId: 301838
|
|
dashedName: problem-2-even-fibonacci-numbers
|
|
---
|
|
|
|
# --description--
|
|
|
|
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:
|
|
|
|
<div style='text-align: center;'>1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...</div>
|
|
|
|
By considering the terms in the Fibonacci sequence whose values do not exceed `n`, find the sum of the even-valued terms.
|
|
|
|
# --hints--
|
|
|
|
`fiboEvenSum(10)` should return a number.
|
|
|
|
```js
|
|
assert(typeof fiboEvenSum(10) === 'number');
|
|
```
|
|
|
|
Your function should return an `even` value.
|
|
|
|
```js
|
|
assert.equal(fiboEvenSum(10) % 2 === 0, true);
|
|
```
|
|
|
|
Your function should sum the even-valued Fibonacci numbers: `fiboEvenSum(8)` should return 10.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(8), 10);
|
|
```
|
|
|
|
`fiboEvenSum(10)` should return 10.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(10), 10);
|
|
```
|
|
|
|
`fiboEvenSum(34)` should return 44.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(34), 44);
|
|
```
|
|
|
|
`fiboEvenSum(60)` should return 44.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(60), 44);
|
|
```
|
|
|
|
`fiboEvenSum(1000)` should return 798.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(1000), 798);
|
|
```
|
|
|
|
`fiboEvenSum(100000)` should return 60696.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(100000), 60696);
|
|
```
|
|
|
|
`fiboEvenSum(4000000)` should return 4613732.
|
|
|
|
```js
|
|
assert.strictEqual(fiboEvenSum(4000000), 4613732);
|
|
```
|
|
|
|
# --seed--
|
|
|
|
## --seed-contents--
|
|
|
|
```js
|
|
function fiboEvenSum(n) {
|
|
|
|
return true;
|
|
}
|
|
```
|
|
|
|
# --solutions--
|
|
|
|
```js
|
|
const fiboEvenSum = (number) => {
|
|
if (number <= 1) {
|
|
return 0;
|
|
} else {
|
|
let evenSum = 0,
|
|
prevFibNum = 1,
|
|
fibNum = 2; // According to problem description our Fibonacci series starts with 1, 2
|
|
for (let i = 2; fibNum <= number; i++) {
|
|
if (fibNum % 2 == 0) {
|
|
evenSum += fibNum;
|
|
}
|
|
[prevFibNum, fibNum] = [fibNum, prevFibNum + fibNum];
|
|
}
|
|
return evenSum;
|
|
}
|
|
};
|
|
```
|