day one in go

01/main.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"time"
+)
+
+func lookahead(line string, i, peek int) string {
+	if len(line) > i+peek-1 {
+		return line[i : i+peek]
+	}
+	return ""
+}
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
+}
+
+func makeScanner(test bool) *bufio.Scanner {
+	var f *os.File
+	if test {
+		f, _ = os.Open("inputs/testinput")
+	} else {
+		f, _ = os.Open("inputs/input")
+	}
+	reader := bufio.NewReader(f)
+	return bufio.NewScanner(reader)
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+
+	sum := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		var first, last rune
+		for _, c := range line {
+			switch c {
+			case '1', '2', '3', '4', '5', '6', '7', '8', '9':
+				if first == 0 {
+					first = c
+				}
+				last = c
+			}
+		}
+		sum += 10*(int(first)-48) + int(last) - 48 // direct ASCII translation
+	}
+	fmt.Println(sum)
+}
+
+func partTwo() {
+	scanner := makeScanner(false)
+
+	sum := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		var first, last rune
+		for i, c := range line {
+			switch {
+			case c == '1' || lookahead(line, i, 3) == "one":
+				if first == 0 {
+					first = '1'
+				}
+				last = '1'
+			case c == '2' || lookahead(line, i, 3) == "two":
+				if first == 0 {
+					first = '2'
+				}
+				last = '2'
+			case c == '3' || lookahead(line, i, 5) == "three":
+				if first == 0 {
+					first = '3'
+				}
+				last = '3'
+
+			case c == '4' || lookahead(line, i, 4) == "four":
+				if first == 0 {
+					first = '4'
+				}
+				last = '4'
+			case c == '5' || lookahead(line, i, 4) == "five":
+				if first == 0 {
+					first = '5'
+				}
+				last = '5'
+			case c == '6' || lookahead(line, i, 3) == "six":
+				if first == 0 {
+					first = '6'
+				}
+				last = '6'
+			case c == '7' || lookahead(line, i, 5) == "seven":
+				if first == 0 {
+					first = '7'
+				}
+				last = '7'
+			case c == '8' || lookahead(line, i, 5) == "eight":
+				if first == 0 {
+					first = '8'
+				}
+				last = '8'
+			case c == '9' || lookahead(line, i, 4) == "nine":
+				if first == 0 {
+					first = '9'
+				}
+				last = '9'
+			}
+		}
+		sum += 10*(int(first)-48) + int(last) - 48
+	}
+	fmt.Println(sum)
+}