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@hhimanshu
Created June 7, 2015 04:40
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P02 (*) Find the last but one element of a list.
package com.learner.s99
/**
* (*) Find the last but one element of a list.
* Example:
* scala> penultimate(List(1, 1, 2, 3, 5, 8))
* res0: Int = 5
*/
object P02 {
def penultimate(input: List[Any]): Any = penultimate(input, None, None)
private def penultimate(input: List[Any], secondLast: Any, last: Any): Any = input match {
case List() => secondLast
case head :: tail => penultimate(tail, last, head)
}
}
package com.learner.s99
import com.learner.s99.P02.penultimate
import org.scalatest.{FlatSpec, MustMatchers}
class P02Spec extends FlatSpec
with MustMatchers {
behavior of "A List"
it must "return 7 in List(1,2,3,4,5,6,7,8) as penultimate element" in {
penultimate(List(1, 2, 3, 4, 5, 6, 7, 8)) must equal(7)
}
it must "return None in List(1) as penultimate element" in {
penultimate(List(1)) must be(None)
}
it must "return 'beta' in List(alpha, beta, gamma) as penultimate element" in {
penultimate(List("alpha","beta", "gamma")) must equal("beta")
}
it must "return 1 in List(1, two) as penultimate element" in {
penultimate(List(1, "two")) must equal(1)
}
it must "return None empty List as penultimate element" in {
penultimate(List()) must be(None)
}
}
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