Day 1b

day01/day01.go

@@ -8,11 +8,47 @@ import (
 	"strings"
 )
 
+const digits = "0123456789"
+
+func words() [10]string {
+	return [10]string{"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"}
+}
+
+func firstDigit(input string) string {
+	var result string
+	loc := len(input)
+	if index := strings.IndexAny(input, "0123456789"); index != -1 {
+		loc = index
+		result = string([]rune(input)[index])
+	}
+	for key, value := range words() {
+		if index := strings.Index(input, value); index != -1 && index <= loc {
+			loc = index
+			result = strconv.Itoa(key)
+		}
+	}
+	return result
+}
+
+func lastDigit(input string) string {
+	var result string
+	loc := -1
+	if index := strings.LastIndexAny(input, "0123456789"); index != -1 {
+		loc = index
+		result = string([]rune(input)[index])
+	}
+	for key, value := range words() {
+		if index := strings.LastIndex(input, value); index != -1 && index >= loc {
+			loc = index
+			result = strconv.Itoa(key)
+		}
+	}
+	return result
+}
+
 func getCalibrationValue(input string) int {
-	firstIdx := strings.IndexAny(input, "0123456789")
-	lastIdx := strings.LastIndexAny(input, "0123456789")
-	first := string([]rune(input)[firstIdx])
-	last := string([]rune(input)[lastIdx])
+	first := firstDigit(input)
+	last := lastDigit(input)
 	output, _ := strconv.Atoi(first + last)
 	return output
 }