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