Add functionality to parse and add spelled out numbers

day1/example2.txt

@@ -0,0 +1,7 @@
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen

day1/part2.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+func readInput() string {
+	stdin, err := io.ReadAll(os.Stdin)
+
+	if err != nil {
+		panic(err)
+	}
+	str := string(stdin)
+	return str
+}
+
+func parseSpelledDigit(input string) string {
+	digits := map[string]string{
+		"one":   "1",
+		"two":   "2",
+		"three": "3",
+		"four":  "4",
+		"five":  "5",
+		"six":   "6",
+		"seven": "7",
+		"eight": "8",
+		"nine":  "9",
+	}
+	i, ok := digits[input]
+	if ok == false {
+		return "-1"
+	}
+	return i
+}
+
+func addSDStrings(input1 string, input2 string) string {
+	num1 := parseSpelledDigit(input1)
+	if num1 == "-1" {
+		num1 = input1
+	}
+	num2 := parseSpelledDigit(input2)
+	if num2 == "-1" {
+		num2 = input2
+	}
+	num_str := num1 + num2
+	return num_str
+}
+
+func main() {
+	lines := strings.Split(readInput(), "\n")
+	re := regexp.MustCompile(`(one|two|three|four|five|six|seven|eight|nine|\d)`)
+	var answer int
+	for _, l := range lines {
+		matches := re.FindAllString(l, -1)
+		matches_len := len(matches)
+		if matches_len == 0 {
+			continue
+		}
+		first := matches[0]
+		last := matches[matches_len-1]
+		num_str := first + " " + last
+		num, err := strconv.Atoi(num_str)
+		if err != nil {
+			num_str = addSDStrings(first, last)
+			num, err = strconv.Atoi(num_str)
+			if err != nil {
+				log.Fatalln(err)
+				continue
+			}
+
+		}
+		answer = answer + num
+		fmt.Println(l, first, last, num)
+	}
+	fmt.Println(answer)
+}