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advent-of-code-2023
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Add solution for day 9 part 2

master
Nick Krichevsky 2023-12-09 13:33:54 -05:00
parent 587d832294
commit f3b957628e
1 changed files with 13 additions and 0 deletions
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13
day9/main.go
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@ -4,6 +4,7 @@ import (
"fmt" "fmt"
"io" "io"
"os" "os"
"slices"
"strconv" "strconv"
"strings" "strings"
) )
@ -35,6 +36,7 @@ func main() {
} }
fmt.Printf("Part 1: %d\n", part1(histories)) fmt.Printf("Part 1: %d\n", part1(histories))
fmt.Printf("Part 2: %d\n", part2(histories))
} }
func part1(histories [][]int) int { func part1(histories [][]int) int {
@ -46,6 +48,17 @@ func part1(histories [][]int) int {
return total 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 // predictNextValue calculates the next item in the sequence by using the nth differences
func predictNextValue(history []int) int { func predictNextValue(history []int) int {
if allEqual(history, 0) { if allEqual(history, 0) {