adventOfCodeDay2Pt2.kt

fun getLevels(report: String): List<Int> = report
  .trim()
  .split(" ".toRegex())
  .filter { it.length > 0 }
  .map { it.trim().toInt() }
  
  fun isSafe(levels: List<Int>): Boolean {
  // if all diffs are in range, and go all up or all down, it's safe
  // iterate through and taking once of the numbers out to
  return (0 until levels.size).any { idx ->
    val list = levels.toMutableList().apply { this.removeAt(idx) }
      .zipWithNext() { a, b -> b - a } // convert levels to diffs
    val allPositive = { list.all { it in (1..3) } }
    val allNegative = { list.all { it in (-3)..(-1) } }
    allPositive() || allNegative()
  }
}
  
import java.io.File
import java.io.IOException

fun readFileContents(filePath: String): String {
  return try {
    val file = File(filePath)
    file.readText()
  } catch (e: IOException) {
    "Error reading file: ${e.message}"
  }
}

readFileContents("./input.txt")
  .lines()
  .filter { isSafe(getLevels(it)) }
  .size
  .run { println(this) }