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solutions/day2/day2.go

@@ -0,0 +1,166 @@
+package day2
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+
+	"golang.org/x/exp/utf8string"
+)
+
+type Move = int
+
+const (
+	Rock     Move = 1
+	Paper         = 2
+	Scissors      = 3
+)
+
+type Result = int
+
+const (
+	Loss Result = 0
+	Tie         = 3
+	Win         = 6
+)
+
+func score(opponent Move, us Move) int {
+	switch opponent {
+	case Rock:
+		switch us {
+		case Rock:
+			return Rock + Tie
+		case Paper:
+			return Paper + Win
+		case Scissors:
+			return Scissors + Loss
+		}
+
+	case Paper:
+		switch us {
+		case Rock:
+			return Rock + Loss
+		case Paper:
+			return Paper + Tie
+		case Scissors:
+			return Scissors + Win
+		}
+
+	case Scissors:
+		switch us {
+		case Rock:
+			return Rock + Win
+		case Paper:
+			return Paper + Loss
+		case Scissors:
+			return Scissors + Tie
+		}
+	}
+
+	fmt.Println("PANIC: Unknown combo: them", opponent, "us", us)
+	return 0
+}
+
+func compute_move(opponent Move, goal Result) Move {
+	switch opponent {
+	case Rock:
+		switch goal {
+		case Loss:
+			return Scissors
+		case Tie:
+			return Rock
+		case Win:
+			return Paper
+		}
+
+	case Paper:
+		switch goal {
+		case Loss:
+			return Rock
+		case Tie:
+			return Paper
+		case Win:
+			return Scissors
+		}
+
+	case Scissors:
+		switch goal {
+		case Loss:
+			return Paper
+		case Tie:
+			return Scissors
+		case Win:
+			return Rock
+		}
+	}
+
+	fmt.Println("PANIC: Unknown combo: them", opponent, "goal", goal)
+	return 0
+
+}
+
+func move(r rune) Move {
+	switch r {
+	case 'A':
+		return Rock
+	case 'B':
+		return Paper
+	case 'C':
+		return Scissors
+	case 'X':
+		return Rock
+	case 'Y':
+		return Paper
+	case 'Z':
+		return Scissors
+	}
+	fmt.Println("PANIC: Unknown character", r)
+	return 0
+}
+
+func result(r rune) Result {
+	switch r {
+	case 'X':
+		return Loss
+	case 'Y':
+		return Tie
+	case 'Z':
+		return Win
+	}
+	fmt.Println("PANIC: Unknown character for result", r)
+	return 99
+}
+
+func Run(filename string) {
+	file, err := os.Open(filename)
+
+	if err != nil {
+		fmt.Println("Error opening file:", err)
+		return
+	}
+
+	scanner := bufio.NewScanner(file)
+	scanner.Split(bufio.ScanLines)
+
+	var total_score_base int = 0
+	var total_score_extended int = 0
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		utf8 := utf8string.NewString(line)
+
+		opponent := move(utf8.At(0))
+		us := move(utf8.At(2))
+
+		total_score_base += score(opponent, us)
+
+		target := result(utf8.At(2))
+		computed_move := compute_move(opponent, target)
+		total_score_extended += score(opponent, computed_move)
+	}
+
+	file.Close()
+
+	fmt.Println("Total initial score is", total_score_base)
+	fmt.Println("Total score with back compute is", total_score_extended)
+}