commit 5440938450c4f686a61b0d3acbec74f0858fa0ba
parent f0ffa82775a10d7fcc735c700966c446aba33c07
Author: bsandro <email@bsandro.tech>
Date: Fri, 9 Dec 2022 06:36:21 +0000
Day 09 part 1
Diffstat:
| A | day09/input.txt | | | 2000 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | day09/main.go | | | 126 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | day09/sample.txt | | | 8 | ++++++++ |
3 files changed, 2134 insertions(+), 0 deletions(-)
diff --git a/day09/input.txt b/day09/input.txt
@@ -0,0 +1,2000 @@
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diff --git a/day09/main.go b/day09/main.go
@@ -0,0 +1,126 @@
+package main
+
+import (
+ "bufio"
+ "fmt"
+ "log"
+ "os"
+ "math"
+)
+
+func abs(a int) int {
+ return int(math.Abs(float64(a)))
+}
+
+type Pos struct {
+ x, y int
+}
+func (p Pos) Diff(o Pos) Pos {
+ var diff Pos
+ diff.x = p.x - o.x
+ diff.y = p.y - o.y
+ return diff
+}
+func (p Pos) Dist(o Pos) int {
+ // returns maximum of distances by X or Y axis
+ diff := p.Diff(o)
+ dx := abs(diff.x)
+ dy := abs(diff.y)
+ if dx > dy {
+ return dx
+ } else {
+ return dy
+ }
+}
+type Rope struct {
+ head, tail Pos
+ visited []Pos
+}
+func (r *Rope) AddVisited(p Pos) {
+ add := true
+ for _, v := range r.visited {
+ if v.x == p.x && v.y == p.y {
+ add = false
+ break
+ }
+ }
+ if add {
+ r.visited = append(r.visited, p)
+ }
+}
+func (r *Rope) MoveTail() bool {
+ if r.head.Dist(r.tail) > 1 {
+ d := r.head.Diff(r.tail)
+ if abs(d.x)==2 {
+ d.x /= 2
+ }
+ if abs(d.y)==2 {
+ d.y /= 2
+ }
+ r.tail.x += d.x
+ r.tail.y += d.y
+ return true
+ }
+ return false
+}
+func (r *Rope) Step(dx, dy int) {
+ r.head.x += dx
+ r.head.y += dy
+ if r.MoveTail() {
+ r.AddVisited(r.tail)
+ }
+}
+func (r *Rope) Move(dir string, dist int) {
+ //fmt.Println("direction:", dir, "distance:", dist)
+ for d:=0; d<dist; d++ {
+ switch dir {
+ case "L":
+ r.Step(-1, 0)
+ case "R":
+ r.Step(1, 0)
+ case "U":
+ r.Step(0, 1)
+ case "D":
+ r.Step(0, -1)
+ default:
+ log.Fatal("Invalid direction", dir)
+ }
+ }
+}
+
+func main() {
+ if len(os.Args) > 1 {
+ day09(os.Args[1])
+ } else if len(os.Args) == 1 {
+ fmt.Printf("usage: %s inputfile.txt\n", os.Args[0])
+ } else {
+ fmt.Println("No input data")
+ }
+}
+
+func day09(input_file string) {
+ fmt.Printf("day 09 input filename: %s\n", input_file)
+ input, err := os.Open(input_file)
+ if err != nil {
+ log.Fatal(err)
+ }
+ defer input.Close()
+ scanner := bufio.NewScanner(input)
+ var rope Rope
+ rope.AddVisited(rope.tail)
+ for scanner.Scan() {
+ in := scanner.Text()
+ var dir string
+ var dist int
+ found, err := fmt.Sscanf(in, "%s %d", &dir, &dist)
+ if err != nil || found != 2 {
+ log.Fatal("Invalid input string", in, err)
+ }
+ rope.Move(dir, dist)
+ }
+ if err = scanner.Err(); err != nil {
+ log.Fatal(err)
+ }
+
+ fmt.Printf("visited: %d\n", len(rope.visited))
+}
diff --git a/day09/sample.txt b/day09/sample.txt
@@ -0,0 +1,8 @@
+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2
