2.2 KiB
2.2 KiB
title | id | challengeType | videoUrl | localeTitle |
---|---|---|---|---|
Entropy | 599d15309e88c813a40baf58 | 5 | 熵 |
Description
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("0")</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("01")</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("0123")</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("01234567")</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("0123456789abcdef")</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("1223334444")</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