Burrows–Wheeler transform: Difference between revisions

=={{header|Scala}}==

{{trans|Kotlin}}

<lang scala>import scala.collection.mutable.ArrayBuffer

object BWT {

val STX = '\u0002'

val ETX = '\u0003'

def bwt(s: String): String = {

if (s.contains(STX) || s.contains(ETX)) {

throw new RuntimeException("String can't contain STX or ETX")

}

var ss = STX + s + ETX

// val table = Array<String>(ss.length) { ss.substring(it) + ss.substring(0, it) }

var table = new ArrayBuffer[String]()

(0 until ss.length).foreach(_ => {

table += ss

ss = ss.substring(1) + ss.charAt(0)

})

// return String(table.map { it[it.lastIndex] }.toCharArray())

table.sorted.map(a => a.last).mkString

}

def ibwt(r: String): String = {

var table = Array.fill(r.length)("")

(0 until r.length).foreach(_ => {

(0 until r.length).foreach(i => {

table(i) = r.charAt(i) + table(i)

})

table = table.sorted

})

table.indices.foreach(i => {

val row = table(i)

if (row.last == ETX) {

return row.substring(1, row.length - 1)

}

})

""

}

def makePrintable(s: String): String = {

s.replace(STX, '^').replace(ETX, '|')

}

def main(args: Array[String]): Unit = {

val tests = Array("banana",

"appellee",

"dogwood",

"TO BE OR NOT TO BE OR WANT TO BE OR NOT?",

"SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES",

"\u0002ABC\u0003"

)

tests.foreach(test => {

println(makePrintable(test))

print(" --> ")

try {

val t = bwt(test)

println(makePrintable(t))

val r = ibwt(t)

printf(" --> %s\n", r)

} catch {

case e: Exception => printf("ERROR: %s\n", e.getMessage)

}

println()

})

}

}</lang>

{{out}}

<pre>banana

--> |annb^aa

--> banana

appellee

--> |e^elplepa

--> appellee

dogwood

--> |do^oodwg

--> dogwood

TO BE OR NOT TO BE OR WANT TO BE OR NOT?

--> |?OOORREEETTRTW BBB ATTT NNOOONOO^

--> TO BE OR NOT TO BE OR WANT TO BE OR NOT?

SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES

--> |STEXYDST.E.IXXIIXXSSMPPS.B..EE.^.USFXDIIOIIIT

--> SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES

^ABC|

--> ERROR: String can't contain STX or ETX</pre>