day 25

25/main.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+)
+
+func mustAtoi(line string) int {
+	i, _ := strconv.Atoi(line)
+	return i
+}
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	fmt.Printf("p1: %s\n", 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 parseSNAFU(str string) int {
+	num := 0
+	place := 1
+	for i := len(str) - 1; i >= 0; i-- {
+		switch str[i] {
+		case '2':
+			num += place * 2
+		case '1':
+			num += place
+		case '0':
+			// noop
+		case '-':
+			num -= place
+		case '=':
+			num -= place * 2
+		default:
+			panic("oh no")
+		}
+		place *= 5
+	}
+	return num
+}
+
+func toSNAFU(normal int) string {
+	num := ""
+	digits := []string{"0", "1", "2", "=", "-"}
+	for {
+		num = digits[normal%5] + num
+		if normal == 0 {
+			return num
+		}
+		normal = (normal + 2) / 5
+	}
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+	sum := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		sum += parseSNAFU(line)
+	}
+	fmt.Println(toSNAFU(sum)[1:])
+}