65 lines
2.2 KiB
Markdown
65 lines
2.2 KiB
Markdown
---
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title: Entropy
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id: 599d15309e88c813a40baf58
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challengeType: 5
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videoUrl: ''
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localeTitle: 熵
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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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testString: 'assert(typeof entropy === "function", "<code>entropy</code> is a 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, "<code>entropy("0")</code> should return <code>0</code>");'
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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, "<code>entropy("01")</code> should return <code>1</code>");'
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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, "<code>entropy("0123")</code> should return <code>2</code>");'
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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, "<code>entropy("01234567")</code> should return <code>3</code>");'
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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, "<code>entropy("0123456789abcdef")</code> should return <code>4</code>");'
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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, "<code>entropy("1223334444")</code> should return <code>1.8464393446710154</code>");'
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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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</section>
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