adventofcode/2021/day21/main.go

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2021-12-21 17:14:16 +00:00
package main
import (
"fmt"
h "git.bullercodeworks.com/brian/adventofcode/helpers"
)
func main() {
inp := h.StdinToStringSlice()
var starting []int
for i := range inp {
starting = append(starting, int(inp[i][len(inp[i])-1]-'0'))
}
part1(starting)
fmt.Println()
part2(starting)
}
type player struct {
number int
position, score int
}
func (p *player) move(spaces int) {
p.position = (p.position + spaces) % 10
if p.position == 0 {
p.position = 10
}
p.score += p.position
}
type die struct {
value int
rolls int
}
func (d *die) roll() int {
d.rolls++
d.value++
if d.value > 100 {
d.value = 1
}
return d.value
}
func part1(pos []int) {
var players []player
for i := range pos {
players = append(players, player{number: i + 1, position: pos[i]})
}
die := die{value: 0}
pTurn := 0
for players[0].score < 1000 && players[1].score < 1000 {
turn := die.roll() + die.roll() + die.roll()
players[pTurn].move(turn)
pTurn = (pTurn + 1) % len(players)
}
var loser player
for i := range players {
if loser.number == 0 || players[i].score < loser.score {
loser = players[i]
}
}
fmt.Println("# Part 1")
fmt.Printf("Player %d loses, score %d\n", (loser.number), loser.score*die.rolls)
}
func part2(pos []int) {
var players []player
for i := range pos {
players = append(players, player{number: i + 1, position: pos[i]})
}
diracIt(pos[0], pos[1])
}
type gameState struct {
p1, p2 int
s1, s2 int
}
// Run the games with the dirac die.
func diracIt(p1, p2 int) {
move := func(pos, roll int) int {
pos += roll
pos = pos % 10
if pos == 0 {
return 10
}
return pos
}
states := map[gameState]int64{{p1, p2, 0, 0}: 1}
rolls := map[int]int64{}
for r1 := 1; r1 <= 3; r1++ {
for r2 := 1; r2 <= 3; r2++ {
for r3 := 1; r3 <= 3; r3++ {
rolls[r1+r2+r3] += 1
}
}
}
var p1w, p2w int64 = 0, 0
for len(states) != 0 {
for turn := 1; turn <= 2; turn++ {
nextStates := map[gameState]int64{}
for state, count := range states {
for roll, rCount := range rolls {
p1, p2 := state.p1, state.p2
s1, s2 := state.s1, state.s2
n := count * rCount
if turn == 1 {
p1 = move(p1, roll)
s1 += p1
if s1 > 20 {
p1w += n
} else {
nextStates[gameState{p1, p2, s1, s2}] += n
}
} else {
p2 = move(p2, roll)
s2 += p2
if s2 > 20 {
p2w += n
} else {
nextStates[gameState{p1, p2, s1, s2}] += n
}
}
}
}
states = nextStates
}
}
fmt.Println("# Part 2")
fmt.Printf("Player 1 Wins: %d\nPlayer 2 Wins: %d\n", p1w, p2w)
}