minor improvement to day 18

Author: Zordid

src/main/kotlin/Day18_OperationOrder.kt

@@ -22,7 +22,7 @@ class Day18 : Day(18, title = "Operation Order") {
  private fun String.evaluatePart2(): Long {
  trim().toLongOrNull()?.let { return it }
 
- val tokens = tokenize()
+ val tokens = tokenize().toMutableList()
  val operationsInOrder = listOf<Pair<String, Long.(Long) -> Long>>("+" to Long::plus, "*" to Long::times)
  operationsInOrder.forEach { (operator, operation) ->
  while (tokens.contains(operator)) {
@@ -37,7 +37,7 @@ class Day18 : Day(18, title = "Operation Order") {
  return tokens.single().toLong()
  }
 
- private fun String.tokenize(): MutableList<String> {
+ private fun String.tokenize(): List<String> {
  var s = this.trim()
  val tokens = mutableListOf<String>()
  do {