AOC2023-D1

aoc2023_d1.go

package d1

import (
	"bufio"
	"io"
	"regexp"
	"unicode/utf8"
)

func Must(err error) {
	if err != nil {
		panic(err)
	}
}

var intMap = map[string]int{
	"one":   1,
	"two":   2,
	"three": 3,
	"four":  4,
	"five":  5,
	"six":   6,
	"seven": 7,
	"eight": 8,
	"nine":  9,
}
var revIntMap = map[string]int{
	"eno":   1,
	"owt":   2,
	"eerht": 3,
	"ruof":  4,
	"evif":  5,
	"xis":   6,
	"neves": 7,
	"thgie": 8,
	"enin":  9,
}

func Reverse(s string) string {
	size := len(s)
	buf := make([]byte, size)
	for start := 0; start < size; {
		r, n := utf8.DecodeRuneInString(s[start:])
		start += n
		utf8.EncodeRune(buf[size-start:], r)
	}
	return string(buf)
}

func d1_1(r io.Reader) interface{} {
	reNums := regexp.MustCompile(`(\d{1})`)

	fileScanner := bufio.NewScanner(r)
	fileScanner.Split(bufio.ScanLines)

	totalSum := 0
	for fileScanner.Scan() {
		databytes := fileScanner.Bytes()
		foundNums := reNums.FindAll(databytes, -1)
		num1 := (int(foundNums[0][0]) - 48) * 10
		num2 := int(foundNums[len(foundNums)-1][0]) - 48
		totalSum += (num1 + num2)
	}
	return totalSum
}

func d1_2(r io.Reader) int {
	reNums := regexp.MustCompile(`(one|two|three|four|five|six|seven|eight|nine|\d)`)
	revNums := regexp.MustCompile(`(eno|owt|eerht|ruof|evif|xis|neves|thgie|enin|\d)`)

	//numbers := make([]int, 0, 1000)
	fileScanner := bufio.NewScanner(r)
	fileScanner.Split(bufio.ScanLines)

	totalSum := 0
	for fileScanner.Scan() {
		databytes := fileScanner.Text()
		first := reNums.FindString(databytes)
		last := revNums.FindString(Reverse(databytes))
		var num1 int
		if len(first) == 1 {
			num1 = (int(first[0]) - 48) * 10
		} else {
			num1 = intMap[first] * 10
		}

		var num2 int
		if len(last) == 1 {
			num2 = int(last[0]) - 48
		} else {
			num2 = revIntMap[last]
		}
		//numbers = append(numbers, num1+num2)
		totalSum += (num1 + num2)
	}
	return totalSum
}