Created
May 9, 2013 20:07
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A small algorithm to find the indexof the first element superior or equal to the given value (in an ordered sequence)
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#!/bin/sh | |
exec scala "$0" "$@" | |
!# | |
import scala.annotation.tailrec | |
// --------------------------------------------------- | |
def searchFirstGreaterOrEqual[T<%Ordered[T]](seq: Seq[T], value: T):Option[Int] = { | |
@tailrec | |
def binarysearch(left:Int, right:Int):Option[Int] = { | |
if (seq(left)>=value) Some(left) | |
if (seq(right)<value) None // Not found | |
else { | |
(left+right)/2 match { | |
case m if seq(m)==value => Some(m) | |
case m if seq(m)>value => | |
if (m!=left) binarysearch(left, m) else Some(m) | |
case m if seq(m)<value => | |
if (m<right) binarysearch(m+1, right) | |
else None // Not found | |
} | |
} | |
} | |
binarysearch(0, seq.size-1) | |
} | |
// --------------------------------------------------- | |
val l1=List(10,20,30,50,100) | |
def testWith[T<%Ordered[T]](seq:Seq[T], value:T) { | |
val result = searchFirstGreaterOrEqual(seq, value) | |
println(s"${value}->${result}") | |
} | |
println(s"""Results with ${l1.mkString(" ")}""") | |
testWith(l1, 0) | |
testWith(l1, 15) | |
testWith(l1, 20) | |
testWith(l1, 55) | |
testWith(l1, 150) |
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