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76 lines
1.1 KiB
Markdown
76 lines
1.1 KiB
Markdown
---
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id: 597f24c1dda4e70f53c79c81
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title: 斐波那契序列
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challengeType: 1
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forumTopicId: 302268
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dashedName: fibonacci-sequence
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---
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# --description--
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Write a function to generate the <code>n<sup>th</sup></code> Fibonacci number.
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第 <code>n<sup>th</sup></code> 个斐波那契数由下式给出：
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<code>F<sub>n</sub> = F<sub>n-1</sub> + F<sub>n-2</sub></code>
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级数的前两项是 0 和 1。
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因此，该系列是：0, 1, 1, 2, 3, 5, 8, 13...
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# --hints--
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`fibonacci` 应该是一个函数。
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```js
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assert(typeof fibonacci === 'function');
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```
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`fibonacci(2)` 应该返回一个数字。
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```js
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assert(typeof fibonacci(2) == 'number');
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```
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`fibonacci(3)` 应该返回 2。
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```js
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assert.equal(fibonacci(3), 2);
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```
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`fibonacci(5)` 应该返回 5。
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```js
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assert.equal(fibonacci(5), 5);
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```
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`fibonacci(10)` 应该返回 55。
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```js
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assert.equal(fibonacci(10), 55);
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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 fibonacci(n) {
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}
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```
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# --solutions--
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```js
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function fibonacci(n) {
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let a = 0, b = 1, t;
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while (--n >= 0) {
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t = a;
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a = b;
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b += t;
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}
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return a;
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}
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```
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