a very "good enough for AOC" kinda solution

2022/day02/main.go

@@ -0,0 +1,178 @@
+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)
+	}
+}
+
+const (
+	Win  = 6
+	Loss = 0
+	Draw = 3
+
+	Rock     = 1
+	Paper    = 2
+	Scissors = 3
+)
+
+// this code is heinoussssss
+// there's some kind of cheeky map to circular LL nodes to determine if you won or lost
+// but there are so few branches to handle that it's faster to just code it manually...
+
+func part1(input string) int {
+	lines := parseInput(input)
+
+	// opp choices: ABC rock-paper-scissors
+	// my choices:  XYZ rock-paper-scissors
+	choices := map[string]int{
+		"X": Rock,
+		"Y": Paper,
+		"Z": Scissors,
+	}
+
+	totalScore := 0
+	for _, l := range lines {
+		if _, ok := choices[l[1]]; !ok {
+			panic("choice not in choices map")
+		}
+		totalScore += choices[l[1]]
+		switch l[1] {
+		case "X": // i played rock
+			switch l[0] {
+			case "A":
+				totalScore += Draw
+			case "B":
+				totalScore += Loss
+			case "C":
+				totalScore += Win
+			default:
+				panic("unacceptable opp choice " + l[0])
+			}
+		case "Y": // i played paper
+			switch l[0] {
+			case "A": // rock
+				totalScore += Win
+			case "B": // paper
+				totalScore += Draw
+			case "C": // scissors
+				totalScore += Loss
+			default:
+				panic("unacceptable opp choice " + l[0])
+			}
+		case "Z": // i played scissors
+			switch l[0] {
+			case "A": // rock
+				totalScore += Loss
+			case "B": // paper
+				totalScore += Win
+			case "C": // scissors
+				totalScore += Draw
+			default:
+				panic("unacceptable opp choice " + l[0])
+			}
+		}
+	}
+
+	return totalScore
+}
+
+func part2(input string) int {
+	/*
+		second column is result, not your choice
+		X -> you lose
+		Y -> draw
+		Z -> win
+	*/
+	lines := parseInput(input)
+
+	winningScores := map[string]int{
+		"X": Loss,
+		"Y": Draw,
+		"Z": Win,
+	}
+
+	totalScore := 0
+	for _, l := range lines {
+		if _, ok := winningScores[l[1]]; !ok {
+			panic("unacceptable result " + l[1])
+		}
+		totalScore += winningScores[l[1]]
+		// switch on opp choice instead
+		switch l[0] {
+		case "A": // opp: rock
+			switch l[1] {
+			case "X": // lose
+				totalScore += Scissors
+			case "Y": // draw
+				totalScore += Rock
+			case "Z": // win
+				totalScore += Paper
+			default:
+				panic("unacceptable choice " + l[1])
+			}
+		case "B": // opp: paper
+			switch l[1] {
+			case "X": // lose
+				totalScore += Rock
+			case "Y": // draw
+				totalScore += Paper
+			case "Z": // win
+				totalScore += Scissors
+			default:
+				panic("unacceptable choice " + l[1])
+			}
+		case "C": // opp: scissors
+			switch l[1] {
+			case "X": // lose
+				totalScore += Paper
+			case "Y": // draw
+				totalScore += Scissors
+			case "Z": // win
+				totalScore += Rock
+			default:
+				panic("unacceptable choice " + l[1])
+			}
+		}
+	}
+
+	return totalScore
+}
+
+func parseInput(input string) (ans [][]string) {
+	for _, line := range strings.Split(input, "\n") {
+		ans = append(ans, strings.Split(line, " "))
+	}
+	return ans
+}