92 lines
1.8 KiB
Go
92 lines
1.8 KiB
Go
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package main
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import (
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"fmt"
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"strings"
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h "git.bullercodeworks.com/brian/adventofcode/helpers"
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)
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func main() {
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inp := h.StdinToStringSlice()
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solve(inp)
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}
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func solve(input []string) {
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var p1result, p2result int
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for i := range input {
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s := NewSeq(i, input[i])
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s.stabilize()
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s.predict()
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v2, v1 := s.value()
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p1result += v1
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p2result += v2
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}
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fmt.Println("# Part 1")
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fmt.Println(p1result)
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fmt.Println()
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fmt.Println("# Part 2")
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fmt.Println(p2result)
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}
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type Seq struct {
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row int
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history [][]int
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}
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func NewSeq(row int, input string) *Seq {
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s := Seq{row: row}
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pts := strings.Fields(input)
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first := []int{}
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for i := range pts {
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first = append(first, h.Atoi(pts[i]))
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}
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s.history = append(s.history, first)
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return &s
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}
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func (s *Seq) value() (int, int) {
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return s.history[0][0], s.history[0][len(s.history[0])-1]
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}
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func (s *Seq) predict() {
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s.history[len(s.history)-1] = append(s.history[len(s.history)-1], 0)
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s.history[len(s.history)-1] = append([]int{0}, s.history[len(s.history)-1]...)
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if len(s.history) > 1 {
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for i := len(s.history) - 2; i >= 0; i-- {
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nV := s.history[i][len(s.history[i])-1] + s.history[i+1][len(s.history[i+1])-1]
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s.history[i] = append(s.history[i], nV)
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// And now go backwards
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pV := s.history[i][0] - s.history[i+1][0]
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s.history[i] = append([]int{pV}, s.history[i]...)
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}
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}
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}
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func (s *Seq) stabilize() {
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for !s.isStable() {
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s.iterate()
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}
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}
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func (s *Seq) iterate() {
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idx := len(s.history) - 1
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l := len(s.history[idx]) - 1
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var next []int
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for i := range s.history[idx] {
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if i < l {
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next = append(next, s.history[idx][i+1]-s.history[idx][i])
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}
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}
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s.history = append(s.history, next)
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}
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func (s *Seq) isStable() bool {
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for _, v := range s.history[len(s.history)-1] {
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if v != 0 {
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return false
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}
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}
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return true
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}
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