day25... thankfully didnt need crazy mod math

2022/day25/main.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) string {
+	snafuNums := strings.Split(input, "\n")
+	// sum of the fuel requirements
+	// power of 5...
+	// 2  is 2
+	// 1  is 1
+	// 0  is 0
+	// -1 is -
+	// -2 is =
+	sum := ""
+	for _, n := range snafuNums {
+		sum = addSnafu(sum, n)
+	}
+
+	return sum
+}
+
+func addSnafu(one, two string) string {
+	// reversed...
+	split1, split2 := strings.Split(one, ""), strings.Split(two, "")
+	var reversed1, reversed2 []string
+	for i := len(split1) - 1; i >= 0; i-- {
+		reversed1 = append(reversed1, split1[i])
+	}
+	for i := len(split2) - 1; i >= 0; i-- {
+		reversed2 = append(reversed2, split2[i])
+	}
+
+	longer, shorter := reversed1, reversed2
+	if len(longer) < len(shorter) {
+		longer, shorter = shorter, longer
+	}
+
+	charToVal := map[string]int{
+		"=": -2,
+		"-": -1,
+		"0": 0,
+		"1": 1,
+		"2": 2,
+	}
+	valToChar := map[int]string{
+		-2: "=",
+		-1: "-",
+		0:  "0",
+		1:  "1",
+		2:  "2",
+	}
+
+	ans := make([]int, len(longer)+1)
+	for i := 0; i < len(longer); i++ {
+		sum := charToVal[longer[i]]
+		if i < len(shorter) {
+			sum += charToVal[shorter[i]]
+		}
+		ans[i] += sum
+		if ans[i] > 2 {
+			ans[i] -= 5
+			ans[i+1]++
+		} else if ans[i] < -2 {
+			ans[i] += 5
+			ans[i+1]--
+		}
+	}
+
+	for ans[len(ans)-1] == 0 {
+		ans = ans[:len(ans)-1]
+	}
+
+	snafu := ""
+	for _, a := range ans {
+		snafu = valToChar[a] + snafu
+	}
+	return snafu
+}
+
+func part2(input string) string {
+	return ":)"
+}

2022/day25/main_test.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	_ "embed"
+	"testing"
+)
+
+var example = `1=-0-2
+12111
+2=0=
+21
+2=01
+111
+20012
+112
+1=-1=
+1-12
+12
+1=
+122`
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  "2=-1=0",
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  "2----0=--1122=0=0021",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  ":)",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}