123 lines
2.0 KiB
Go
123 lines
2.0 KiB
Go
package main
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import (
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"bufio"
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_ "embed"
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"fmt"
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"slices"
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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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// var log = aoc.Log
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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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func run(scan *bufio.Scanner) (*result, error) {
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var matches []int
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for scan.Scan() {
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text := scan.Text()
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status, text, ok := strings.Cut(text, " ")
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if !ok {
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continue
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}
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grouping := aoc.SliceMap(aoc.Atoi, strings.Split(text, ",")...)
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pattern := []rune(status)
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missing := countQuestion(pattern)
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s := spring{pattern: pattern, grouping: grouping, missingNo: missing}
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matches = append(matches, s.findMatches())
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}
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return &result{valuePT1: aoc.Sum(matches...)}, nil
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}
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type spring struct {
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pattern []rune
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grouping []int
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missingNo int
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}
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func (s *spring) findMatches() int {
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matches := 0
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for _, pattern := range s.genPatterns() {
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pattern := []rune(pattern)
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target := make([]rune, len(s.pattern))
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i := 0
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for j, r := range s.pattern {
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if r == '?' {
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target[j] = pattern[i]
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i++
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continue
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}
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target[j] = r
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}
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if slices.Equal(countGroupings(target), s.grouping) {
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matches++
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}
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}
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return matches
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}
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func (s *spring) genPatterns() []string {
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buf := &strings.Builder{}
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combinations := aoc.Power2(s.missingNo)
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lis := make([]string, 0, combinations)
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for i := 0; i < combinations; i++ {
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for b := 0; b < s.missingNo; b++ {
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if i>>b&0b1 == 1 {
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buf.WriteRune('#')
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} else {
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buf.WriteRune('.')
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}
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}
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lis = append(lis, buf.String())
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buf.Reset()
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}
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return lis
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}
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func countQuestion(pattern []rune) int {
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count := 0
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for _, r := range pattern {
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if r == '?' {
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count++
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}
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}
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return count
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}
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func countGroupings(pattern []rune) []int {
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var groupings []int
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inGroup := false
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for _, r := range pattern {
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if r == '#' {
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if !inGroup {
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groupings = append(groupings, 0)
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}
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inGroup = true
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groupings[len(groupings)-1]++
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}
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if inGroup && r != '#' {
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inGroup = false
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}
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}
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return groupings
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}
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