2018-10-10 22:03:03 +00:00
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---
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id: 599d15309e88c813a40baf58
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challengeType: 5
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videoUrl: ''
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2020-10-01 15:54:21 +00:00
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title: 熵
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2018-10-10 22:03:03 +00:00
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---
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## Description
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<section id="description">任务: <p>计算给定输入字符串的香农熵H. </p><p>给定谨慎的随机变量$ X $,它是$ N $“符号”(总字符)的字符串,由$ n $个不同的字符组成(对于二进制,n = 2),位/符号中X的香农熵是: </p><p> $ H_2(X)= - \ sum_ {i = 1} ^ n \ frac {count_i} {N} \ log_2 \ left(\ frac {count_i} {N} \ right)$ </p><p>其中$ count_i $是字符$ n_i $的计数。 </p></section>
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## Instructions
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<section id="instructions">
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>entropy</code>是一种功能。
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2020-02-17 16:40:55 +00:00
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testString: assert(typeof entropy === 'function');
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- text: <code>entropy("0")</code>应该返回<code>0</code>
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testString: assert.equal(entropy('0'), 0);
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- text: <code>entropy("01")</code>应该返回<code>1</code>
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testString: assert.equal(entropy('01'), 1);
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- text: <code>entropy("0123")</code>应该返回<code>2</code>
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testString: assert.equal(entropy('0123'), 2);
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- text: <code>entropy("01234567")</code>应该返回<code>3</code>
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testString: assert.equal(entropy('01234567'), 3);
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- text: <code>entropy("0123456789abcdef")</code>应返回<code>4</code>
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testString: assert.equal(entropy('0123456789abcdef'), 4);
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- text: <code>entropy("1223334444")</code>应返回<code>1.8464393446710154</code>
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testString: assert.equal(entropy('1223334444'), 1.8464393446710154);
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2018-10-10 22:03:03 +00:00
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function entropy (s) {
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// Good luck!
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}
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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2020-08-13 15:24:35 +00:00
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/section>
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