2022 Day 9 Complete!
This commit is contained in:
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package main
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import (
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"fmt"
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"os"
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"strings"
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"time"
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h "git.bullercodeworks.com/brian/adventofcode/helpers"
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)
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var sleepTime = (time.Second / 5)
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var minx, miny, maxx, maxy int
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func main() {
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inp := h.StdinToStringSlice()
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watch := len(os.Args) > 1 && strings.HasPrefix(os.Args[1], "-w")
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if watch {
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if strings.Contains(os.Args[1], "=") {
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pts := strings.Split(os.Args[1], "=")
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sleepTime = (time.Second / time.Duration(h.Atoi(pts[1])))
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}
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}
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simulate(inp, 10, watch)
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}
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func buildInstructions(inp []string) []byte {
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var inst []byte
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for i := range inp {
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dir, count := inp[i][0], h.Atoi(inp[i][2:])
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for j := 0; j < count; j++ {
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inst = append(inst, dir)
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}
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}
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return inst
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}
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func simulate(inp []string, knotCount int, watch bool) {
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if watch {
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fmt.Print(h.CLEAR_SCREEN)
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}
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visited := make(map[h.Coordinate]bool)
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inst := buildInstructions(inp)
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var knots []h.Coordinate
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for i := 0; i < knotCount; i++ {
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knots = append(knots, h.Coordinate{X: 0, Y: 0})
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}
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if watch {
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fmt.Println("# Part 1")
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printVisits(visited, knots)
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}
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for i, dir := range inst {
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moveHead(dir, knots)
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visited[knots[len(knots)-1]] = true
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if watch {
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time.Sleep(sleepTime)
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fmt.Print(h.CLEAR_SCREEN)
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fmt.Printf("# Part 1 (%d/%d)\n", i, len(inst))
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printVisits(visited, knots)
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}
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}
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if watch {
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time.Sleep(sleepTime)
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fmt.Print(h.CLEAR_SCREEN)
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}
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fmt.Println("# Part 1")
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if watch {
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printVisits(visited, knots)
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}
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fmt.Printf("Tail visited %d positions\n", len(visited))
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}
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func moveHead(dir byte, knots []h.Coordinate) {
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prevKnots := make([]h.Coordinate, len(knots))
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copy(prevKnots, knots)
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switch dir {
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case 'U':
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knots[0] = knots[0].North()
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case 'R':
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knots[0] = knots[0].East()
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case 'D':
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knots[0] = knots[0].South()
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case 'L':
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knots[0] = knots[0].West()
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}
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if knots[0].X < minx {
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minx = knots[0].X
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}
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if knots[0].X > maxx {
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maxx = knots[0].X
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}
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if knots[0].Y < miny {
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miny = knots[0].Y
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}
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if knots[0].Y > maxy {
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maxy = knots[0].Y
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}
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for i := 1; i < len(knots); i++ {
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// Go through all knots and check if any need to move
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if !knots[i].Equals(knots[i-1]) && !knots[i].Adjacent(knots[i-1]) {
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if knots[i].X == knots[i-1].X {
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// Same column
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if knots[i].Y < knots[i-1].Y {
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knots[i].Y++
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} else {
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knots[i].Y--
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}
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} else if knots[i].Y == knots[i-1].Y {
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// Save row
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if knots[i].X < knots[i-1].X {
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knots[i].X++
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} else {
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knots[i].X--
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}
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} else {
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// Not in the same row or column
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if knots[i].X < knots[i-1].X {
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knots[i].X++
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} else {
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knots[i].X--
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}
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if knots[i].Y < knots[i-1].Y {
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knots[i].Y++
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} else {
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knots[i].Y--
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}
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}
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} else {
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// If one knot didn't need to move, none behind it will
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break
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}
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}
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}
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func printVisits(m map[h.Coordinate]bool, knots []h.Coordinate) {
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for y := miny; y <= maxy; y++ {
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for x := minx; x <= maxx; x++ {
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var isKnot bool
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for i := range knots {
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if knots[i].X == x && knots[i].Y == y {
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isKnot = true
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var bt byte
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if i == 0 {
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bt = 'H'
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} else {
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bt = '0' + byte(i)
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}
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fmt.Print(string(bt))
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break
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}
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}
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if !isKnot {
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if v, ok := m[h.Coordinate{X: x, Y: y}]; ok && v {
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fmt.Print("#")
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} else {
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fmt.Print(".")
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}
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}
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}
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fmt.Println()
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}
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fmt.Printf("Bridge: %s\n", knots)
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fmt.Println()
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}
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@ -0,0 +1,311 @@
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Advent of Code
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• [About]
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• [Events]
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• [Shop]
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• [Settings]
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• [Log Out]
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br0xen (AoC++) 16*
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0.0.0.0:2022
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• [Calendar]
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• [AoC++]
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• [Sponsors]
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• [Leaderboard]
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• [Stats]
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Our sponsors help make Advent of Code possible:
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King - At King, we create unforgettable games (like Candy Crush) that are loved around the world. Join us to bring
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moments of magic to hundreds of millions of people every single day!
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--- Day 9: Rope Bridge ---
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This rope bridge creaks as you walk along it. You aren't sure how old it is, or whether it can even support your weight.
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It seems to support the Elves just fine, though. The bridge spans a gorge which was carved out by the massive river far
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below you.
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You step carefully; as you do, the ropes stretch and twist. You decide to distract yourself by modeling rope physics;
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maybe you can even figure out where not to step.
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Consider a rope with a knot at each end; these knots mark the head and the tail of the rope. If the head moves far
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enough away from the tail, the tail is pulled toward the head.
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Due to nebulous reasoning involving Planck lengths, you should be able to model the positions of the knots on a
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two-dimensional grid. Then, by following a hypothetical series of motions (your puzzle input) for the head, you can
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determine how the tail will move.
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Due to the aforementioned Planck lengths, the rope must be quite short; in fact, the head (H) and tail (T) must always
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be touching (diagonally adjacent and even overlapping both count as touching):
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....
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.TH.
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....
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....
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.H..
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..T.
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....
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...
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.H. (H covers T)
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...
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If the head is ever two steps directly up, down, left, or right from the tail, the tail must also move one step in that
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direction so it remains close enough:
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..... ..... .....
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.TH.. -> .T.H. -> ..TH.
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..... ..... .....
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... ... ...
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.T. .T. ...
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.H. -> ... -> .T.
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... .H. .H.
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... ... ...
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Otherwise, if the head and tail aren't touching and aren't in the same row or column, the tail always moves one step
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diagonally to keep up:
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..... ..... .....
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..... ..H.. ..H..
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..H.. -> ..... -> ..T..
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.T... .T... .....
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..... ..... .....
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..... ..... .....
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..... ..... .....
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..H.. -> ...H. -> ..TH.
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.T... .T... .....
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..... ..... .....
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You just need to work out where the tail goes as the head follows a series of motions. Assume the head and the tail both
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start at the same position, overlapping.
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For example:
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R 4
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U 4
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L 3
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D 1
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R 4
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D 1
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L 5
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R 2
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This series of motions moves the head right four steps, then up four steps, then left three steps, then down one step,
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and so on. After each step, you'll need to update the position of the tail if the step means the head is no longer
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adjacent to the tail. Visually, these motions occur as follows (s marks the starting position as a reference point):
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== Initial State ==
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......
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......
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......
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......
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H..... (H covers T, s)
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== R 4 ==
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......
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......
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......
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......
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TH.... (T covers s)
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......
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......
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......
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......
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sTH...
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......
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......
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......
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......
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s.TH..
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......
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......
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......
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......
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s..TH.
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== U 4 ==
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......
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......
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......
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....H.
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s..T..
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......
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......
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....H.
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....T.
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s.....
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......
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....H.
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....T.
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......
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s.....
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....H.
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....T.
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......
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......
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s.....
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== L 3 ==
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...H..
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....T.
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......
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......
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s.....
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..HT..
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......
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......
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......
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s.....
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.HT...
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......
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......
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......
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s.....
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== D 1 ==
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..T...
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.H....
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......
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......
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s.....
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== R 4 ==
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..T...
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..H...
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......
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......
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s.....
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..T...
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...H..
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......
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......
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s.....
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......
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...TH.
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......
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......
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s.....
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......
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....TH
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......
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......
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s.....
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== D 1 ==
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......
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....T.
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.....H
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......
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s.....
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== L 5 ==
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......
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....T.
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....H.
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......
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s.....
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......
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....T.
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...H..
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......
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s.....
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......
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......
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..HT..
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......
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s.....
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......
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......
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.HT...
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......
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s.....
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......
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......
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HT....
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......
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s.....
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== R 2 ==
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......
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......
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.H.... (H covers T)
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......
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s.....
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......
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......
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.TH...
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......
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s.....
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After simulating the rope, you can count up all of the positions the tail visited at least once. In this diagram, s
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again marks the starting position (which the tail also visited) and # marks other positions the tail visited:
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..##..
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...##.
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.####.
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....#.
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s###..
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So, there are 13 positions the tail visited at least once.
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Simulate your complete hypothetical series of motions. How many positions does the tail of the rope visit at least once?
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To begin, get your puzzle input.
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Answer: _____________________ [ [Submit] ]
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You can also [Shareon Twitter Mastodon] this puzzle.
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References
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Visible links
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. https://adventofcode.com/
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. https://adventofcode.com/2022/about
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. https://adventofcode.com/2022/events
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. https://teespring.com/stores/advent-of-code
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. https://adventofcode.com/2022/settings
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. https://adventofcode.com/2022/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2022/support
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. https://adventofcode.com/2022
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. https://adventofcode.com/2022
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. https://adventofcode.com/2022/support
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. https://adventofcode.com/2022/sponsors
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. https://adventofcode.com/2022/leaderboard
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. https://adventofcode.com/2022/stats
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. https://adventofcode.com/2022/sponsors
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. https://careers.king.com/
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. https://en.wikipedia.org/wiki/Planck_units#Planck_length
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. https://adventofcode.com/2022/day/9/input
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. https://twitter.com/intent/tweet?text=%22Rope+Bridge%22+%2D+Day+9+%2D+Advent+of+Code+2022&url=https%3A%2F%2Fadventofcode%2Ecom%2F2022%2Fday%2F9&related=ericwastl&hashtags=AdventOfCode
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. javascript:void(0);
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@ -0,0 +1,8 @@
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R 4
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U 4
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L 3
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D 1
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R 4
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D 1
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L 5
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R 2
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@ -0,0 +1,8 @@
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R 5
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U 8
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L 8
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D 3
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R 17
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D 10
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L 25
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U 20
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@ -97,3 +97,13 @@ func (c Coordinate) Distance(t Coordinate) int {
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func (c Coordinate) Equals(c2 Coordinate) bool {
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return c.X == c2.X && c.Y == c2.Y
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}
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func (c Coordinate) Adjacent(c2 Coordinate) bool {
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return c2.Equals(c.North()) ||
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c2.Equals(c.NE()) ||
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c2.Equals(c.East()) ||
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c2.Equals(c.SE()) ||
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c2.Equals(c.South()) ||
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c2.Equals(c.SW()) ||
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c2.Equals(c.West()) ||
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c2.Equals(c.NW())
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}
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