126 lines
2.7 KiB
Go
126 lines
2.7 KiB
Go
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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// type definitions
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type Direction int
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const (
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Up Direction = iota + 1
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Down
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Left
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Right
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)
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type state struct {
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field [][]rune
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guard_x int
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guard_y int
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direction Direction
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}
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func new_state(text string) *state {
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lines := strings.Split(text, "\n")
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field := make([][]rune, len(lines))
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guard := [2]int{-1,-1}
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for y := range lines {
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field[y] = []rune(lines[y])
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for x, r := range field[y] {
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if r == '^' {
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guard = [2]int{x, y}
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field[y][x] = '.'
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}
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}
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}
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s := state{field: field, guard_x: guard[0], guard_y: guard[1], direction: Up}
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return &s
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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 add_non_duplicate(slice [][2]int, elem [2]int) [][2]int {
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for _, e := range slice {
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if e == elem { return slice }
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}
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return append(slice, elem)
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}
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// simulation functions
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func iter(s *state) *state {
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new_guard_x := s.guard_x
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new_guard_y := s.guard_y
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// try to move
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switch {
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case s.direction == Up:
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new_guard_y--
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case s.direction == Down:
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new_guard_y++
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case s.direction == Left:
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new_guard_x--
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case s.direction == Right:
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new_guard_x++
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}
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// if guard is outside of the field
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if new_guard_x < 0 || new_guard_y < 0 || new_guard_x >= len(s.field[0]) || new_guard_y >= len(s.field) {
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new_guard_x = -1
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new_guard_y = -1
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} else if s.field[new_guard_y][new_guard_x] == '#' {
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// correct if path is blocked
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switch {
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case s.direction == Up:
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new_guard_y++
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s.direction = Right
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new_guard_x++
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case s.direction == Down:
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new_guard_y--
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s.direction = Left
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new_guard_x--
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case s.direction == Left:
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new_guard_x++
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s.direction = Up
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new_guard_y--
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case s.direction == Right:
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new_guard_x--
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s.direction = Down
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new_guard_y++
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}
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}
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// set new guard coordinates
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s.guard_x = new_guard_x
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s.guard_y = new_guard_y
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return s
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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 := string(dat[:len(dat) - 1])
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stateobj := new_state(dat_str)
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distinct_pos := make([][2]int, 0)
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for stateobj.guard_x >= 0 {
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distinct_pos = add_non_duplicate(distinct_pos, [2]int{stateobj.guard_x, stateobj.guard_y})
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stateobj = iter(stateobj)
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}
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fmt.Println(len(distinct_pos))
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}
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