day(02): solve

Signed-off-by: Matej Focko <me@mfocko.xyz>

inputs/day02/sample.txt

@@ -0,0 +1,6 @@
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9

src/Day02.kt

@@ -0,0 +1,34 @@
+class Day02(
+    inputType: String,
+) : Day<Int, Int>() {
+    private val reports: List<List<Int>> =
+        readInput(2, inputType)
+            .map { line ->
+                line.split(" ").map { it.toInt() }
+            }.toList()
+
+    override fun precompute() {
+        // [TODO] Implement precomputation
+    }
+
+    private fun isCorrect(report: List<Int>): Boolean {
+        val isIncreasing = report[0] < report[1]
+        return report.windowed(2).fold(true) { acc, (x, y) ->
+            acc && maxOf(x - y, y - x) in 1..3 && ((isIncreasing && x < y) || (!isIncreasing && x > y))
+        }
+    }
+
+    override fun part1(): Int = reports.count(::isCorrect)
+
+    override fun part2(): Int =
+        reports.count { report ->
+            report.indices.any { skip ->
+                isCorrect(report.filterIndexed { idx, _ -> idx != skip })
+            }
+        }
+}
+
+fun main() {
+    Day02("sample").test(2, 4)
+    Day02("input").run()
+}