Scala function: Check if a list is sorted

Last update on February 06 2025 12:56:14 (UTC/GMT +8 hours)

Write a Scala function to check if a given list is sorted in ascending order.

Before you start!

To solve this problem, you should have a basic understanding of:

• Scala lists and how to define them.
• Comparing elements in a list using relational operators.
• How the sliding method works for iterating over consecutive elements.
• The concept of implicit parameters in Scala.
• Using the forall method to check conditions on all elements in a list.

Try before looking at the solution!

Think about how you can check if a list is sorted in ascending order:

• How can you compare each element with the next one in the list?
• What happens if the list has only one element or is empty?
• How does the Ordering trait help in comparing generic types?
• Can you solve this using recursion or a loop instead of built-in methods?

Sample Solution:

Scala Code:

object ListSortChecker {
  def isSortedAscending[A](list: List[A])(implicit ord: Ordering[A]): Boolean = {
    list.sliding(2).forall { case List(a, b) => ord.lteq(a, b) }
  }

  def main(args: Array[String]): Unit = {
    val list1 = List(1, 2, 3, 4, 5, 6)
    val list2 = List(4, 2, 5, 1, 6, 3)
    println("List1: "+list1)
    println(s"Is List1 is sorted in ascending order? ${isSortedAscending(list1)}")
    println("List2: "+list2)
    println(s"Is List2 is sorted in ascending order? ${isSortedAscending(list2)}")
  }
}

Sample Output:

List1: List(1, 2, 3, 4, 5, 6)
Is List1 is sorted in ascending order? true
List2: List(4, 2, 5, 1, 6, 3)
Is List2 is sorted in ascending order? false

Scala Code Editor :

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