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2.2 KiB

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title	id	challengeType	videoUrl	localeTitle
Entropy	599d15309e88c813a40baf58	5		熵

Description

任务：

计算给定输入字符串的香农熵H.

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：

$ H_2（X）= - \ sum_ {i = 1} ^ n \ frac {count_i} {N} \ log_2 \ left（\ frac {count_i} {N} \ right）$

其中$ count_i $是字符$ n_i $的计数。

Instructions

Tests

tests:
  - text: <code>entropy</code>是一种功能。
    testString: 'assert(typeof entropy === "function", "<code>entropy</code> is a function.");'
  - text: <code>entropy(&quot;0&quot;)</code>应该返回<code>0</code>
    testString: 'assert.equal(entropy("0"), 0, "<code>entropy("0")</code> should return <code>0</code>");'
  - text: <code>entropy(&quot;01&quot;)</code>应该返回<code>1</code>
    testString: 'assert.equal(entropy("01"), 1, "<code>entropy("01")</code> should return <code>1</code>");'
  - text: <code>entropy(&quot;0123&quot;)</code>应该返回<code>2</code>
    testString: 'assert.equal(entropy("0123"), 2, "<code>entropy("0123")</code> should return <code>2</code>");'
  - text: <code>entropy(&quot;01234567&quot;)</code>应该返回<code>3</code>
    testString: 'assert.equal(entropy("01234567"), 3, "<code>entropy("01234567")</code> should return <code>3</code>");'
  - text: <code>entropy(&quot;0123456789abcdef&quot;)</code>应返回<code>4</code>
    testString: 'assert.equal(entropy("0123456789abcdef"), 4, "<code>entropy("0123456789abcdef")</code> should return <code>4</code>");'
  - text: <code>entropy(&quot;1223334444&quot;)</code>应返回<code>1.8464393446710154</code>
    testString: 'assert.equal(entropy("1223334444"), 1.8464393446710154, "<code>entropy("1223334444")</code> should return <code>1.8464393446710154</code>");'

Challenge Seed

function entropy (s) {
  // Good luck!
}

Solution

// solution required

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