From f3b957628eeb700fc7ace18c2c39c8d06ac688ee Mon Sep 17 00:00:00 2001
From: Nick Krichevsky <nick@ollien.com>
Date: Sat, 9 Dec 2023 13:33:54 -0500
Subject: [PATCH] Add solution for day 9 part 2

---
 day9/main.go | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/day9/main.go b/day9/main.go
index 7205a25..83c2100 100644
--- a/day9/main.go
+++ b/day9/main.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"slices"
 	"strconv"
 	"strings"
 )
@@ -35,6 +36,7 @@ func main() {
 	}
 
 	fmt.Printf("Part 1: %d\n", part1(histories))
+	fmt.Printf("Part 2: %d\n", part2(histories))
 }
 
 func part1(histories [][]int) int {
@@ -46,6 +48,17 @@ func part1(histories [][]int) int {
 	return total
 }
 
+func part2(histories [][]int) int {
+	total := 0
+	for _, history := range histories {
+		reversedHistory := slices.Clone(history)
+		slices.Reverse(reversedHistory)
+		total += predictNextValue(reversedHistory)
+	}
+
+	return total
+}
+
 // predictNextValue calculates the next item in the sequence by using the nth differences
 func predictNextValue(history []int) int {
 	if allEqual(history, 0) {