115 lines
2.5 KiB
Go
115 lines
2.5 KiB
Go
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package main
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import (
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"os"
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"fmt"
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"strings"
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)
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// data types
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type Point struct {
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x int16
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y int16
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}
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type Antenna struct {
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point Point
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freq byte
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}
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// general util
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func check(e error) {
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if e != nil { panic(e) }
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}
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func (p Point) Mul(scalar int) Point {
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return Point { x: p.x * int16(scalar), y: p.y * int16(scalar) }
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}
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func (p Point) Add(other Point) Point {
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return Point { x: p.x + other.x, y: p.y + other.y }
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}
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func (p Point) Sub(other Point) Point {
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return Point { x: p.x - other.x, y: p.y - other.y }
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}
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func contains(arr []Point, p Point) bool {
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for _, elem := range arr {
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if elem == p { return true }
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}
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return false
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}
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func addNonDuplicate(arr []Point, p Point) []Point {
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if contains(arr, p) { return arr
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} else { return append(arr, p) }
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}
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func newAntennas(data string) []Antenna {
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/* Reads the puzzle input, return a list of antenna structs.
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*/
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antennas := make([]Antenna, 0, 100)
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for y, line := range strings.Split(data, "\n") {
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for x, char := range []byte(line) {
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if char != '.' {
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antennas = append(antennas, Antenna{ point: Point{x: int16(x), y: int16(y)}, freq: char })
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}
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}
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}
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return antennas
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}
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func antinodes(points [2]Point, n int) []Point {
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/* len(antinodes(..., n)) == 2*n + 2 */
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nodes := make([]Point, 2*n)
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distance := points[0].Sub(points[1])
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for i := 0; i < n; i++ {
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nodes[i] = points[0].Add(distance.Mul(i + 1))
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nodes[i + n] = points[1].Sub(distance.Mul(i + 1))
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}
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nodes = append(nodes, points[0])
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nodes = append(nodes, points[1])
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return nodes
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}
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// main loop
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func main() {
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// read in file
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dat, err := os.ReadFile("data.txt")
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check(err)
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dat_str := strings.TrimSpace(string(dat))
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lines := strings.Split(dat_str, "\n")
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height, width := int16(len(lines)), int16(len(lines[0]))
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antennas := newAntennas(dat_str)
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pairs := make([][2]Point, 0)
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for _, ant1 := range antennas {
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for _, ant2 := range antennas {
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if ant1.freq == ant2.freq && ant1.point != ant2.point {
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pairs = append(pairs, [2]Point{ant1.point, ant2.point})
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}
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}
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}
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nodes := make([]Point, 0, len(pairs) * 2)
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for _, pair := range pairs {
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ns := antinodes(pair, 100)
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for _, n := range ns {
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if n.x >= 0 && n.x < width && n.y >= 0 && n.y < height {
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nodes = addNonDuplicate(nodes, n)
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}
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}
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}
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fmt.Println(len(nodes))
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}
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