Created
April 27, 2012 14:25
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/** Find the minimum amount of smoke (second) and resulting color (first) | |
by splitting the sequence at every possible position, | |
given `lookup` contains the best mix for subsequence. */ | |
def minSmokeMixtureSingle(s: Seq[Int], lookup: Map[Seq[Int],(Int,Int)]): (Int,Int) = | |
if(s.size == 1) | |
(s(0),0) | |
else if(s.size == 2) | |
mix(s(0),s(1)) | |
else { | |
val splits = (1 to (s.size - 1)).map(s.splitAt) | |
val mixes = splits.map{ case (s1,s2) => | |
val (c1,sm1) = lookup(s1) | |
val (c2,sm2) = lookup(s2) | |
val (newColor,newSmoke) = mix(c1,c2) | |
(newColor, newSmoke + sm1 + sm2) | |
} | |
mixes.minBy(_._2) | |
} | |
def mix(m1: Int, m2: Int): (Int,Int) = ((m1+m2) % 100, m1*m2) | |
def minSmokeMixture(s: Seq[Int]) = { | |
//create the mixture sequences with increasing length | |
val windows = for(windowSize <- 1 to s.size; | |
window <- s.sliding(windowSize) ) yield window | |
//go over the sequences and compute the lookup-table | |
val lookup = windows.foldLeft(Map.empty[Seq[Int],(Int,Int)]){case (lu,seq) => lu + (seq -> minSmokeMixtureSingle(seq,lu))} | |
//simply lookup the result | |
lookup(s) | |
} | |
println(minSmokeMixture(Seq(18, 19))) | |
println(minSmokeMixture(Seq(40, 60, 20))) |
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