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package main
import (
"bytes"
"fmt"
"io"
"log"
"os"
)
type round struct {
opponent shape
player shape
}
type roundOutcome struct {
lost int
draw int
won int
}
var outcome roundOutcome = roundOutcome{
lost: 0,
draw: 3,
won: 6,
}
type shape rune
const (
opponentRock, playerRock shape = iota + 'A', iota + 'X'
opponentPaper, playerPaper
opponentScissors, playerScissors
)
func shapePoints(p shape) int {
return int((p - playerRock + 1) * 1)
}
func loseDrawWin(o shape) (shape, shape, shape) {
switch o {
case opponentRock:
return playerScissors, playerRock, playerPaper
case opponentPaper:
return playerRock, playerPaper, playerScissors
case opponentScissors:
return playerPaper, playerScissors, playerRock
default:
return 0, 0, 0
}
}
func outcomePoints(r round) int {
player := int(r.player - playerPaper)
opponent := int(r.opponent - opponentPaper)
if player == opponent {
return 3
}
if player+opponent == 0 && player < opponent {
return 6
} else if player+opponent == 0 && player > opponent {
return 0
}
if player < opponent {
return 0
} else {
return 6
}
}
func outcomePointsCheating(p shape) int {
switch p {
case playerRock:
return 0
case playerPaper:
return 3
case playerScissors:
return 6
default:
return 0
}
}
func shapePointsCheating(r round) int {
lose, draw, win := loseDrawWin(r.opponent)
switch outcomePointsCheating(r.player) {
case 0:
return shapePoints(lose)
case 3:
return shapePoints(draw)
case 6:
return shapePoints(win)
default:
return 0
}
}
func countRounds(f io.Reader, buf []byte) (int, error) {
count := 0
for {
i, err := f.Read(buf)
count += bytes.Count(buf[:i], []byte{'\n'})
switch {
case err == io.EOF:
return count, nil
case err != nil:
log.Fatal("Error reading input file")
return count, err
}
}
}
// A very verbose way to read lines into rounds without the bufio package
func getRounds(f io.Reader, buf []byte, rounds []round) []round {
r := 0
for {
n, err := f.Read(buf)
for i := 0; i < n; i += 4 {
o := shape(buf[i])
p := shape(buf[i+2])
if playerRock <= p && p <= playerScissors {
rounds[r].player = p
}
if opponentRock <= o && o <= opponentScissors {
rounds[r].opponent = o
}
if rounds[r].player == 0 || rounds[r].opponent == 0 {
rounds[r] = rounds[len(rounds)-1]
rounds = rounds[:len(rounds)-1]
}
r++
}
if err == io.EOF {
return rounds
}
}
}
func main() {
f, err := os.Open("day2.txt")
if err != nil {
log.Fatal("could not open input file")
}
var buf []byte = make([]byte, 32*1024)
count, err := countRounds(f, buf)
f.Seek(0, 0)
var rounds []round = make([]round, count)
rounds = getRounds(f, buf, rounds)
points := 0
for _, r := range rounds {
points += shapePoints(r.player)
points += outcomePoints(r)
}
fmt.Println("first part: ", points)
points = 0
for _, r := range rounds {
points += shapePointsCheating(r)
points += outcomePointsCheating(r.player)
}
fmt.Println("second part: ", points)
}
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