feat(aoc-2023): day 09 part 1 and part 2

Author: markkovari

2023/src/main/scala/com/markkovari/adventofcode/day09.scala

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+package com.markkovari.adventofcode.day09
+
+type History = List[Long]
+
+def parse(input: String): Seq[Seq[Int]] =
+  input.linesIterator
+    .map(_.split(' ').map(_.toInt).toSeq)
+    .toSeq
+
+def extrapolate(xs: Seq[Int]): Int =
+  if xs.forall(_ == xs.head)
+  then xs.head
+  else
+    xs.last + extrapolate(
+      xs.tail
+        .lazyZip(xs)
+        .map(_ - _)
+    )
+
+def part1(input: String): Int =
+  parse(input)
+    .map(extrapolate)
+    .sum
+
+def part2(input: String): Int =
+  parse(input)
+    .map(_.reverse)
+    .map(extrapolate)
+    .sum

2023/src/test/resources/9/example_1

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+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45