96 lines
1.6 KiB
Markdown
96 lines
1.6 KiB
Markdown
---
|
||
id: 5900f36f1000cf542c50fe82
|
||
title: '問題 3:最大素數因子'
|
||
challengeType: 5
|
||
forumTopicId: 301952
|
||
dashedName: problem-3-largest-prime-factor
|
||
---
|
||
|
||
# --description--
|
||
|
||
13195 的素數因子是 5、7、13 和 29。
|
||
|
||
求給出數 `number` 的最大素數因子是多少?
|
||
|
||
# --hints--
|
||
|
||
`largestPrimeFactor(2)` 應該返回一個數字。
|
||
|
||
```js
|
||
assert(typeof largestPrimeFactor(2) === 'number');
|
||
```
|
||
|
||
`largestPrimeFactor(2)` 應該返回 2。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(2), 2);
|
||
```
|
||
|
||
`largestPrimeFactor(3)` 應該返回 3。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(3), 3);
|
||
```
|
||
|
||
`largestPrimeFactor(5)` 應該返回 5。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(5), 5);
|
||
```
|
||
|
||
`largestPrimeFactor(7)` 應該返回 7。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(7), 7);
|
||
```
|
||
|
||
`largestPrimeFactor(8)` 應該返回 2。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(8), 2);
|
||
```
|
||
|
||
`largestPrimeFactor(13195)` 應該返回 29。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(13195), 29);
|
||
```
|
||
|
||
`largestPrimeFactor(600851475143)` 應該返回 6857。
|
||
|
||
```js
|
||
assert.strictEqual(largestPrimeFactor(600851475143), 6857);
|
||
```
|
||
|
||
# --seed--
|
||
|
||
## --seed-contents--
|
||
|
||
```js
|
||
function largestPrimeFactor(number) {
|
||
|
||
return true;
|
||
}
|
||
|
||
largestPrimeFactor(13195);
|
||
```
|
||
|
||
# --solutions--
|
||
|
||
```js
|
||
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;
|
||
}
|
||
```
|