aoc-day05-golang.go

package main

import (
	"bufio"
	"flag"
	"fmt"
	"log"
	"os"
	"strings"
	"unicode"
)

func readInput(filename string) string {
	fileHandle, _ := os.Open(filename)
	defer func() {
		if err := fileHandle.Close(); err != nil {
			log.Fatal(err)
		}
	}()
	fileScanner := bufio.NewScanner(fileHandle)

	input := ""
	for fileScanner.Scan() {
		line := fileScanner.Text()
		if len(line) > 0 {
			input = line
		}
	}

	return strings.TrimSpace(input)
}

var file = flag.String("file", "./p1.txt", "file used for input")

func main() {
	flag.Parse()

	input := readInput(*file)

	fmt.Println("Part 1:", part1(input))
	fmt.Println("Part 2:", part2(input))
}

func part1(input string) (int) {
	return len(produce(input))
}

func produce(line string) string {
	for {
		changes := false
		for k, g := range line {
			if k > 0 {
				if unicode.IsLower(g) && unicode.IsUpper(rune(line[k-1])) || unicode.IsLower(rune(line[k-1])) && unicode.IsUpper(g) {
					if strings.ToLower(string(g)) == strings.ToLower(string(line[k-1])) {
						line = line[:k-1] + line[k+1:]
						changes = true
					}
				}
			}
			if changes {
				break
			}
		}
		if !changes {
			break
		}
	}

	return line
}

var alphabet = "abcdefghijklmnopqrstuvwxyz"

func part2(input string) (outcome int) {
	outcome = len(input)
	for _, c := range alphabet {
		check := strings.Replace(strings.Replace(input, string(strings.ToUpper(string(c))), "", -1), string(c), "", -1)
		l := len(produce(check))
		if l < outcome {
			outcome = l
		}
	}

	return outcome
}