160 lines
3.7 KiB
Go
160 lines
3.7 KiB
Go
package main
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import (
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"bufio"
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"fmt"
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"os"
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"unicode"
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"github.com/fatih/color"
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"github.com/thoas/go-funk"
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)
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type EnginePart struct {
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number uint64
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line uint64
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startIndex uint64
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endIndex uint64
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}
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func readFileLines(filename string) ([]string, error) {
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var lines []string
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file, err := os.Open(filename)
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if err != nil {
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return lines, err
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}
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fileScanner := bufio.NewScanner(file)
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fileScanner.Split(bufio.ScanLines)
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for fileScanner.Scan() {
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lines = append(lines, fileScanner.Text())
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}
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return lines, nil
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}
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func getEngineParts(lines *[]string) []EnginePart {
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var result []EnginePart
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var tmpPart EnginePart
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for lineIdx := 0; lineIdx < len(*lines); lineIdx++ {
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line := &(*lines)[lineIdx]
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tmpPart.number = 0
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tmpPart.line = uint64(lineIdx)
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numStarted := false
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for charIdx, char := range *line {
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if unicode.IsDigit(char) {
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if !numStarted {
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tmpPart.startIndex = uint64(charIdx)
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numStarted = true
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}
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tmpPart.number *= 10
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tmpPart.number += uint64(char) - uint64('0')
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} else if numStarted {
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numStarted = false
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tmpPart.endIndex = uint64(charIdx) - 1
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result = append(result, tmpPart)
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tmpPart.number = 0
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}
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}
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if numStarted {
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tmpPart.endIndex = uint64(len(*line)) - 1
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result = append(result, tmpPart)
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tmpPart.number = 0
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}
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}
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return result
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}
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func hasSymbol(line *string, startIndex uint64, endIndex uint64) bool {
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for i := startIndex; i <= endIndex; i++ {
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if (*line)[i] != '.' && !unicode.IsDigit(rune((*line)[i])) {
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return true
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}
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}
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return false
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}
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func getValidEngineParts(parts *[]EnginePart, lines *[]string) []uint64 {
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var validParts []uint64
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for i := 0; i < len(*parts); i++ {
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part := &(*parts)[i]
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startIndex := part.startIndex
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endIndex := part.endIndex
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if startIndex > 0 {
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startIndex--
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}
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if endIndex < uint64(len((*lines)[0]))-1 {
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endIndex++
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}
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for i := part.line - 1; i != part.line+2; i++ {
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if i >= uint64(len(*lines)) {
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continue
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}
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if hasSymbol(&(*lines)[i], startIndex, endIndex) {
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validParts = append(validParts, part.number)
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break
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}
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}
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}
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return validParts
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}
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func hasTwoAdjecent(parts *[]EnginePart, lineIdx uint64, charIdx uint64) (bool, []EnginePart) {
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var result []EnginePart
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for i := 0; i < len(*parts); i++ {
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part := &(*parts)[i]
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if part.line >= lineIdx-1 && part.line <= lineIdx+1 {
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if part.startIndex <= charIdx+1 && part.endIndex >= charIdx-1 {
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result = append(result, *part)
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}
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}
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}
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return len(result) == 2, result
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}
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func getGears(parts *[]EnginePart, lines *[]string) []uint64 {
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var result []uint64
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for lineIdx := 0; lineIdx < len(*lines); lineIdx++ {
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line := &((*lines)[lineIdx])
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for charIdx, char := range *line {
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if char == '*' {
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valid, engineParts := hasTwoAdjecent(parts, uint64(lineIdx), uint64(charIdx))
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if valid {
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result = append(result, engineParts[0].number*engineParts[1].number)
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}
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}
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}
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}
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return result
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}
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func main() {
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redPrint := color.New(color.FgRed)
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yellowPrint := color.New(color.FgYellow)
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if len(os.Args) < 2 {
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redPrint.Fprintln(os.Stderr, "You must provide the input file")
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os.Exit(1)
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}
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lines, err := readFileLines(os.Args[1])
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if err != nil {
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redPrint.Fprintln(os.Stderr, "Could not read input file")
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os.Exit(1)
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}
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engineParts := getEngineParts(&lines)
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validParts := getValidEngineParts(&engineParts, &lines)
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validPartSum := funk.Reduce(validParts, func(acc, elem uint64) uint64 { return acc + elem }, uint64(0))
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fmt.Print("Part 1: ")
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yellowPrint.Print(validPartSum)
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fmt.Println()
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gearRatios := getGears(&engineParts, &lines)
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gearRatiosSum := funk.Reduce(gearRatios, func(acc, elem uint64) uint64 { return acc + elem }, uint64(0))
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fmt.Print("Part 2: ")
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yellowPrint.Print(gearRatiosSum)
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fmt.Println()
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}
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