August 26, 2024
P49 - Gray code.
An n-bit Gray code is a sequence of n-bit strings constructed according to certain rules. Find out the construction rules and write a function to generate Gray codes. For example:
> grayCodes(bits = 1)
[0, 1]
> grayCodes(bits = 2)
[00, 01, 11, 10]
> grayCodes(bits = 3)
[000, 001, 011, 010, 110, 111, 101, 100]kotlin
package org.kotlin99.logic
import com.natpryce.hamkrest.assertion.assertThat
import com.natpryce.hamkrest.equalTo
import org.junit.Test
fun grayCodes(bits: Int): List<String> =
if (bits == 0) listOf("")
else {
val codes = grayCodes(bits - 1)
codes.map { "0$it" } + codes.asReversed().map { "1$it" }
}
class P49Test {
@Test fun `generate Gray code values`() {
assertThat(grayCodes(bits = 1), equalTo(listOf("0", "1")))
assertThat(grayCodes(bits = 2), equalTo(listOf("00", "01", "11", "10")))
assertThat(grayCodes(bits = 3), equalTo(listOf("000", "001", "011", "010", "110", "111", "101", "100")))
}
}
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