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title	id	challengeType	videoUrl	localeTitle
Entropy	599d15309e88c813a40baf58	5		Entropia

Description

Tarefa:

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(&quot;0&quot;)</code> deve retornar <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> deve retornar <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> deve retornar <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> deve retornar <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> deve retornar <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> 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

2.3 KiB Raw Blame History