22afc2a0ca
Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com> Co-authored-by: Kristofer Koishigawa <scissorsneedfoodtoo@gmail.com> Co-authored-by: Beau Carnes <beaucarnes@gmail.com>
2.0 KiB
2.0 KiB
id, challengeType, isHidden, title, forumTopicId
| id | challengeType | isHidden | title | forumTopicId |
|---|---|---|---|---|
| 5900f36f1000cf542c50fe82 | 5 | false | Problem 3: Largest prime factor | 301952 |
Description
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the given number?
Instructions
Tests
tests:
- text: <code>largestPrimeFactor(2)</code> should return a number.
testString: assert(typeof largestPrimeFactor(2) === 'number');
- text: <code>largestPrimeFactor(2)</code> should return 2.
testString: assert.strictEqual(largestPrimeFactor(2), 2);
- text: <code>largestPrimeFactor(3)</code> should return 3.
testString: assert.strictEqual(largestPrimeFactor(3), 3);
- text: <code>largestPrimeFactor(5)</code> should return 5.
testString: assert.strictEqual(largestPrimeFactor(5), 5);
- text: <code>largestPrimeFactor(7)</code> should return 7.
testString: assert.strictEqual(largestPrimeFactor(7), 7);
- text: <code>largestPrimeFactor(8)</code> should return 2.
testString: assert.strictEqual(largestPrimeFactor(8), 2);
- text: <code>largestPrimeFactor(13195)</code> should return 29.
testString: assert.strictEqual(largestPrimeFactor(13195), 29);
- text: <code>largestPrimeFactor(600851475143)</code> should return 6857.
testString: assert.strictEqual(largestPrimeFactor(600851475143), 6857);
Challenge Seed
function largestPrimeFactor(number) {
// Good luck!
return true;
}
largestPrimeFactor(13195);
Solution
const largestPrimeFactor = (number) => {
let largestFactor = number;
for (let i = 2; i <= Math.sqrt(largestFactor); i++) {
if (!(largestFactor % i)) {
let factor = largestFactor / i;
let candidate = largestPrimeFactor(factor);
return i > candidate ? i : candidate;
}
}
return largestFactor;
}