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day3-part1.go
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day3-part1.go
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package main
import (
"bufio"
"fmt"
"log"
"os"
"strconv"
"strings"
)
type point struct {
x int
y int
}
func load() ([][]string, error) {
file, err := os.Open("input.txt")
if err != nil {
return nil, fmt.Errorf("couldn't open file: %v", err)
}
defer file.Close()
vals := [][]string{}
scanner := bufio.NewScanner(file)
for scanner.Scan() {
val := scanner.Text()
v := strings.Split(val, ",")
vals = append(vals, v)
}
return vals, err
}
func up(p point) point {
return point{
x: p.x,
y: p.y - 1,
}
}
func down(p point) point {
return point{
x: p.x,
y: p.y + 1,
}
}
func left(p point) point {
return point{
x: p.x - 1,
y: p.y,
}
}
func right(p point) point {
return point{
x: p.x + 1,
y: p.y,
}
}
type goFunc = func(point) point
func follow(c string, curr point) ([]point, point, error) {
points := []point{}
cc := c[0]
n, err := strconv.Atoi(c[1:])
if err != nil {
return points, curr, err
}
var f goFunc
switch cc {
case 'U':
f = up
case 'D':
f = down
case 'L':
f = left
case 'R':
f = right
default:
return points, curr, fmt.Errorf("unknown command %s", cc)
}
for i := 0; i < n; i++ {
pp := f(curr)
curr = pp
points = append(points, pp)
}
return points, curr, nil
}
func linePoints(line []string) (map[point]struct{}, error) {
points := map[point]struct{}{}
curr := point{0, 0}
for _, c := range line {
var p []point
var err error
p, curr, err = follow(c, curr)
if err != nil {
return points, err
}
for _, pp := range p {
points[pp] = struct{}{}
}
}
return points, nil
}
func getCrossings(l1 map[point]struct{}, l2 map[point]struct{}) []point {
p := []point{}
for pp, _ := range l1 {
if _, ok := l2[pp]; ok {
p = append(p, pp)
}
}
return p
}
func abs(i int) int {
if i < 0 {
return -i
}
return i
}
func getClosest(p []point) (point, int) {
c := p[0]
d := abs(p[0].x) + abs(p[0].y)
for _, pp := range p {
dd := abs(pp.x) + abs(pp.y)
if dd < d {
c = pp
d = dd
}
}
return c, d
}
func main() {
vals, err := load()
if err != nil {
log.Fatalf("Couldn't load nums from file: %v", err)
}
fmt.Println(vals)
l1, err := linePoints(vals[0])
if err != nil {
log.Fatalf("oh no %v", err)
}
l2, err := linePoints(vals[1])
if err != nil {
log.Fatalf("oh no %v", err)
}
fmt.Println(l1)
fmt.Println(l2)
crossings := getCrossings(l1, l2)
fmt.Println(crossings)
closest, distance := getClosest(crossings)
fmt.Println(closest, distance)
}