Advent of Code 2023 - Day 1 Part 2

main.go

package main

import (
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
)

const chars string = "123456789"

func main() {
	f, _ := os.Open("./input")
	defer f.Close()
	buff, _ := io.ReadAll(f)
	rows := strings.SplitAfter(string(buff), "\n")
	total := 0
	for i, row := range rows {
		v := parseValue(row)
		fmt.Printf("Row(%d): %q Value: %d\n", i+1, strings.ReplaceAll(row, "\n", ""), v)
		total += v
	}

	fmt.Printf("Total calibration value is:  %d\n", total)
}

func parseValue(input string) int {
	if len(strings.TrimSpace(input)) == 0 {
		return 0
	}
	iFirst := strings.IndexAny(input, chars)
	iLast := strings.LastIndexAny(input, chars)

	first := ""
	last := ""
	if iFirst > -1 {
		first = input[iFirst : iFirst+1]
	}
	if iLast > -1 {
		last = input[iLast : iLast+1]
	}

	spelled := map[string]string{
		"one":   "1",
		"two":   "2",
		"three": "3",
		"four":  "4",
		"five":  "5",
		"six":   "6",
		"seven": "7",
		"eight": "8",
		"nine":  "9",
	}

	for k, v := range spelled {
		if i := strings.Index(input, k); i >= 0 && i < iFirst {
			first = v
			iFirst = i
			if last == "" {
				last = v
				iLast = i
			}
		}
		if i := strings.LastIndex(input, k); i >= 0 && i > iLast {
			last = v
			iLast = i
			if first == "" {
				first = v
				iFirst = i
			}
		}
	}

	num, _ := strconv.Atoi(fmt.Sprintf("%s%s", first, last))

	return num
}