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day10.go
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day10.go
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package main
import (
"fmt"
"os"
"log"
"bufio"
"sort"
)
var chunkOpeners = []rune("([{<")
var chunkClosers = []rune(")]}>")
var invalidChunkScores = map[rune]int { ')': 3, ']': 57, '}': 1197, '>': 25137 }
var completeScores = map[rune]int { ')': 1, ']': 2, '}': 3, '>': 4 }
type chunkParser struct {
openers []rune
}
func pushRune(runes []rune, r rune) []rune {
updated := make([]rune, len(runes)+1)
updated[0] = r
copy(updated[1:], runes)
return updated
}
func IndexRune(runes []rune, r rune) int {
for i, r2 := range runes {
if r2 == r {
return i
}
}
return -1
}
func ContainsRune(runes []rune, r rune) bool {
return IndexRune(runes, r) != -1
}
func (parser *chunkParser) pushOpener(r rune) {
parser.openers = pushRune(parser.openers, r)
}
func (parser *chunkParser) popOpener() {
parser.openers = parser.openers[1:]
}
func (parser *chunkParser) parse(s string) (int, rune) {
runes := []rune(s)
for offset, r := range runes {
if ContainsRune(chunkOpeners, r) {
parser.pushOpener(r)
} else {
closerIndex := IndexRune(chunkClosers, r)
if chunkOpeners[closerIndex] == parser.openers[0] {
parser.popOpener()
} else {
openerIndex := IndexRune(chunkOpeners, parser.openers[0])
fmt.Printf("Expected %c, but found %c instead.\n", chunkClosers[openerIndex], r)
return offset, r
}
}
}
return len(runes), ' '
}
func (parser *chunkParser) validateChunks(s string) int {
if _, r := parser.parse(s); r != ' ' {
return invalidChunkScores[r]
}
return 0
}
func (parser *chunkParser) completeChunks(s string) string {
if _, r := parser.parse(s); r == ' ' {
complete := make([]rune, len(parser.openers))
for i, opener := range parser.openers {
complete[i] = chunkClosers[IndexRune(chunkOpeners, opener)]
}
return string(complete)
}
return ""
}
func scoresForInput(filename string, score func(string) int) []int {
file, err := os.Open(filename)
if err != nil {
log.Fatal(err)
}
defer file.Close()
scores := make([]int, 0)
scanner := bufio.NewScanner(file)
for scanner.Scan() {
scores = append(scores, score(scanner.Text()))
}
return scores
}
func validateScoreForInput(filename string) int {
scores := scoresForInput(filename, func (input string) int {
parser := &chunkParser{}
return parser.validateChunks(input)
})
total := 0
for _, score := range scores {
total += score
}
return total
}
// iterate through lines
// if validateChunks score > 0, ignore
// otherwise, generate and score completion
func completeScoreForInput(filename string) int {
scores := scoresForInput(filename, func (input string) int {
parser := &chunkParser{}
complete := parser.completeChunks(input)
total := 0
for _, c := range complete {
total = total * 5 + completeScores[c]
}
fmt.Printf("score for %s is %d\n", string(complete), total)
return total
})
nonzero := make([]int, 0)
for _, score := range scores {
if score > 0 {
nonzero = append(nonzero, score)
}
}
sort.Slice(nonzero, func(i, j int) bool { return nonzero[i] < nonzero[j] })
return nonzero[len(nonzero)/2]
}
func main() {
// fmt.Println(validateScoreForInput("day10_input.txt"))
fmt.Println(completeScoreForInput("day10_input.txt"))
}