2018-10-10 22:03:03 +00:00
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id: 5900f3851000cf542c50fe98
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2020-12-16 07:37:30 +00:00
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title: 问题25:1000位斐波纳契数
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2018-10-10 22:03:03 +00:00
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challengeType: 5
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videoUrl: ''
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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Fibonacci序列由递归关系定义:
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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F
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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<sub>n</sub>
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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= F
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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<sub>n-1</sub>
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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- F
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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<sub>n-2</sub>
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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,其中F
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<sub>1</sub>
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= 1且F
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<sub>2</sub>
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= 1。
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因此,前12个学期将是:
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F
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<sub>1</sub>
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= 1
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F
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<sub>2</sub>
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= 1
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F
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<sub>3</sub>
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= 2
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F
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<sub>4</sub>
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= 3
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F
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<sub>5</sub>
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= 5
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F
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<sub>6</sub>
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= 8
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F
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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<sub>7</sub>
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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= 13
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F
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<sub>8</sub>
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= 21
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F
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<sub>9</sub>
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= 34
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F
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<sub>10</sub>
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= 55
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F
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<sub>11</sub>
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= 89
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F
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<sub>12</sub>
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= 144
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第12个学期F
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<sub>12</sub>
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是第一个包含三位数的术语。 Fibonacci序列中包含`n个`数字的第一项的索引是多少?
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# --hints--
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`digitFibonacci(5)`应该返回21。
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```js
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assert.strictEqual(digitFibonacci(5), 21);
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2018-10-10 22:03:03 +00:00
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```
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2020-12-16 07:37:30 +00:00
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`digitFibonacci(10)`应该返回45。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert.strictEqual(digitFibonacci(10), 45);
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```
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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`digitFibonacci(15)`应该返回69。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert.strictEqual(digitFibonacci(15), 69);
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```
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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`digitFibonacci(20)`应该返回93。
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert.strictEqual(digitFibonacci(20), 93);
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2018-10-10 22:03:03 +00:00
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```
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2020-08-13 15:24:35 +00:00
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2020-12-16 07:37:30 +00:00
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# --solutions--
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