2.3 KiB
2.3 KiB
title | id | challengeType | videoUrl | localeTitle |
---|---|---|---|---|
Entropy | 599d15309e88c813a40baf58 | 5 | Entropia |
Description
Calcule a entropia de Shannon H de uma determinada string de entrada.
Dada a variável aleatória discreta $ X $ que é uma cadeia de $ N $ "símbolos" (caracteres totais) consistindo de $ n $ caracteres diferentes (n = 2 para binário), a entropia de Shannon de X em bits / símbolo é:
$ H_2 (X) = - \ sum_ {i = 1} ^ n \ frac {count_i} {N} \ log_2 \ left (\ frac {count_i} {N} \ right) $
onde $ count_i $ é a contagem do caractere $ n_i $.
Instructions
Tests
tests:
- text: <code>entropy</code> é uma função.
testString: 'assert(typeof entropy === "function", "<code>entropy</code> is a function.");'
- text: <code>entropy("0")</code> deve retornar <code>0</code>
testString: 'assert.equal(entropy("0"), 0, "<code>entropy("0")</code> should return <code>0</code>");'
- text: <code>entropy("01")</code> deve retornar <code>1</code>
testString: 'assert.equal(entropy("01"), 1, "<code>entropy("01")</code> should return <code>1</code>");'
- text: <code>entropy("0123")</code> deve retornar <code>2</code>
testString: 'assert.equal(entropy("0123"), 2, "<code>entropy("0123")</code> should return <code>2</code>");'
- text: <code>entropy("01234567")</code> deve retornar <code>3</code>
testString: 'assert.equal(entropy("01234567"), 3, "<code>entropy("01234567")</code> should return <code>3</code>");'
- text: <code>entropy("0123456789abcdef")</code> deve retornar <code>4</code>
testString: 'assert.equal(entropy("0123456789abcdef"), 4, "<code>entropy("0123456789abcdef")</code> should return <code>4</code>");'
- text: <code>entropy("1223334444")</code> deve retornar <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