90 lines
1.6 KiB
Go
90 lines
1.6 KiB
Go
package main
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import (
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"fmt"
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"github.com/jdkaplan/advent-of-code/aoc"
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)
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func main() {
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lines := aoc.Input().ReadLines("day21.txt")
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p1, p2 := parseInput(lines)
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fmt.Println(part1(p1, p2))
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}
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func parseInput(lines []string) (p1, p2 int) {
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aoc.MustScan(lines[0], "Player 1 starting position: %d", &p1)
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aoc.MustScan(lines[1], "Player 2 starting position: %d", &p2)
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return
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}
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func part1(p1, p2 int) int {
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g := NewGame(p1, p2, &DD100{})
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for i := 1; true; i++ {
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hash := g.Turn(i)
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if hash != 0 {
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return hash
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}
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}
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return 0
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}
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type Game struct {
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p1, p2 int
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s1, s2 int
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die Roller
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}
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func NewGame(p1, p2 int, die Roller) *Game {
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return &Game{p1, p2, 0, 0, die}
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}
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func (g *Game) String() string {
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return fmt.Sprintf("P1: %2d, S1: %5d | P1: %2d, S1: %5d", g.p1, g.s1, g.p2, g.s2)
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}
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func (g *Game) Turn(turns int) (hash int) {
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if g.P1() {
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return g.s2 * (6*turns - 3)
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}
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if g.P2() {
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return g.s1 * (6 * turns)
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}
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return 0
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}
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func (g *Game) P1() (won bool) {
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roll := g.die.Roll() + g.die.Roll() + g.die.Roll()
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g.p1 = move(g.p1, roll)
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g.s1 += score(g.p1)
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return g.s1 >= 1000
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}
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func (g *Game) P2() (won bool) {
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roll := g.die.Roll() + g.die.Roll() + g.die.Roll()
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g.p2 = move(g.p2, roll)
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g.s2 += score(g.p2)
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return g.s2 >= 1000
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}
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func move(pos, roll int) int {
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// 0-index for math, 1-index for position.
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return ((pos-1)+roll)%10 + 1
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}
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func score(pos int) int {
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// 0-index for math, 1-index for position.
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return (pos-1)%10 + 1
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}
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type Roller interface {
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Roll() int
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}
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type DD100 struct{ val int }
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func (d *DD100) Roll() int {
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val := d.val
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d.val = (d.val + 1) % 100
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return val + 1
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}
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