142 lines
2.6 KiB
Go
142 lines
2.6 KiB
Go
package main
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import (
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"bufio"
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"cmp"
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"fmt"
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"strconv"
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"strings"
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aoc "go.sour.is/advent-of-code-2023"
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)
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func main() { aoc.MustResult(aoc.Runner(run)) }
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type result struct {
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valuePT1 int
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valuePT2 int
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}
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func (r result) String() string { return fmt.Sprintf("%#v", r) }
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var log = aoc.Log
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func run(scan *bufio.Scanner) (*result, error) {
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var histories [][]int
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var values []int
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var rvalues []int
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for scan.Scan() {
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text := scan.Text()
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if len(text) == 0 {
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continue
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}
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histories = append(histories, nil)
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for _, s := range strings.Fields(text) {
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if i, err := strconv.Atoi(s); err == nil {
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histories[len(histories)-1] = append(histories[len(histories)-1], i)
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}
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}
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log(last(histories...))
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values = append(values, predictNext(last(histories...)))
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rvalues = append(rvalues, predictPrev(last(histories...)))
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}
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log("values", values)
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log("rvalues", rvalues)
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return &result{valuePT1: sum(values...), valuePT2: sum(rvalues...)}, nil
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}
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func predictNext(in []int) int {
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log(" ---- PREDICT NEXT ----")
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defer log(" ----------------------")
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history := makeHistory(in)
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aoc.Reverse(history)
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return predict(history, func(a, b int) int { return a + b })
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}
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func predictPrev(in []int) int {
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log(" ---- PREDICT PREV ----")
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defer log(" ----------------------")
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history := makeHistory(in)
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for i := range history {
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aoc.Reverse(history[i])
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}
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aoc.Reverse(history)
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return predict(history, func(a, b int) int { return b - a })
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}
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func predict(history [][]int, diff func(a, b int) int) int {
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log(" ---- PREDICT ----")
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defer log(" -----------------")
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for i := range history[1:] {
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lastHistory, curHistory := last(history[i]...), last(history[i+1]...)
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history[i+1] = append(history[i+1], diff(lastHistory, curHistory))
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log(lastHistory, curHistory, last(history[i+1]))
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}
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log("last", last(history...))
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return last(last(history...)...)
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}
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func makeHistory(in []int) [][]int {
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var history [][]int
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history = append(history, in)
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for {
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var diffs []int
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current := history[len(history)-1]
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for i := range current[1:] {
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diffs = append(diffs, current[i+1]-current[i])
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}
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history = append(history, diffs)
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log(diffs)
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if max(diffs[0], diffs[1:]...) == 0 && min(diffs[0], diffs[1:]...) == 0 {
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break
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}
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}
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return history
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}
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func max[T cmp.Ordered](a T, v ...T) T {
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for _, b := range v {
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if b > a {
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a = b
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}
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}
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return a
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}
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func min[T cmp.Ordered](a T, v ...T) T {
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for _, b := range v {
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if b < a {
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a = b
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}
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}
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return a
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}
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func sum[T cmp.Ordered](v ...T) T {
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var s T
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for _, a := range v {
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s += a
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}
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return s
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}
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func last[T any](v ...T) T {
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return v[len(v)-1]
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}
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