Add 2021 - Day 7 - Part 2

2021/07/main.kt

@@ -6,10 +6,28 @@ fun main() {
 	
 	val p1 = originalPositions.minOrNull() ?: return
 	val p2 = originalPositions.maxOrNull() ?: return
+	val candidates = p1..p2
 	
-	val cheapestFuel = (p1..p2).minOf { p ->
+	part1(originalPositions, candidates)
+	part2(originalPositions, candidates)
+}
+
+fun part1(originalPositions: IntArray, candidates: IntRange) {
+	val cheapestFuel = candidates.minOf { p ->
 		originalPositions.sumOf { abs(it - p) }
 	}
 	
-	println("Cheapest fuel: $cheapestFuel")
+	println("Cheapest fuel at constant fuel usage: $cheapestFuel")
+}
+
+fun part2(originalPositions: IntArray, candidates: IntRange) {
+	val cheapestFuel = candidates.minOf { p1 ->
+		originalPositions.sumOf { p2 ->
+			abs(p2 - p1).let { steps ->
+				(steps * (steps + 1)) / 2
+			}
+		}
+	}
+	
+	println("Cheapest fuel at polynomial fuel usage: $cheapestFuel")
 }