adventofcode/2023/day23/main.go

package main

import (
	"fmt"
	"os"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := h.StdinToStringSlice()
	if len(os.Args) == 1 || os.Args[1] != "-p2" {
		part1(inp)
	}
	if len(os.Args) == 1 {
		fmt.Println()
	}
	if len(os.Args) == 1 || os.Args[1] != "-p1" {
		part2(inp)
	}
}

var history map[string]int

func part1(input []string) {
	history = make(map[string]int)
	m := h.StringSliceToCoordByteMap(input)
	start, _ := m.FindFirst('.')
	start.Y++
	end, _ := m.FindLast('.')
	fmt.Println("# Part 1")
	fmt.Println(len(findPath(&m, start, end, []h.Coordinate{})))
}

func part2(input []string) {
	history = make(map[string]int)
	m := h.StringSliceToCoordByteMap(input)
	start, _ := m.FindFirst('.')
	start.Y++
	end, _ := m.FindLast('.')
	m.ReplaceAll('^', '.')
	m.ReplaceAll('>', '.')
	m.ReplaceAll('v', '.')
	m.ReplaceAll('<', '.')
	fmt.Println("# Part 2")
	fmt.Println(len(findPath(&m, start, end, []h.Coordinate{})))
}

func findPath(m *h.CoordByteMap, pos h.Coordinate, end h.Coordinate, path []h.Coordinate) []h.Coordinate {
	ret := []h.Coordinate{pos}
	if pos.Equals(end) {
		//printPath(m, pos, path)
		//time.Sleep(time.Second / 20)
		return ret
	}

	path = append(path, pos)
	switch m.Get(pos) {
	case '^':
		if inPath(pos.North(), path) {
			return ret
		} else {
			return append(ret, findPath(m, pos.North(), end, path)...)
		}
	case '>':
		if inPath(pos.East(), path) {
			return ret
		} else {
			return append(ret, findPath(m, pos.East(), end, path)...)
		}
	case 'v':
		if inPath(pos.South(), path) {
			return ret
		} else {
			return append(ret, findPath(m, pos.South(), end, path)...)
		}
	case '<':
		if inPath(pos.West(), path) {
			return ret
		} else {
			return append(ret, findPath(m, pos.West(), end, path)...)
		}
	}

	var longestPath []h.Coordinate
	longest := h.MIN_INT
	for _, chk := range []h.Coordinate{pos.North(), pos.East(), pos.South(), pos.West()} {
		if m.Get(chk) == '#' || inPath(chk, path) || !m.ContainsCoord(chk) {
			continue
		}

		var run bool
		var v int
		if v, run = history[chk.String()]; run {
			run = v < len(path)+1
		}
		if run {
			history[chk.String()] = len(path) + 1
			chkPath := append(ret, findPath(m, chk, end, path)...)
			if inPath(end, chkPath) && len(chkPath) > longest {
				longest = len(chkPath)
				longestPath = chkPath
			}
		}
	}
	return longestPath
}

func inPath(pos h.Coordinate, path []h.Coordinate) bool {
	for _, chk := range path {
		if chk.Equals(pos) {
			return true
		}
	}
	return false
}

func printPath(m *h.CoordByteMap, pos h.Coordinate, path []h.Coordinate) {
	limit := (m.BRY - m.TLY) > 30
	fmt.Print(h.CLEAR_SCREEN)
	for y := m.TLY; y <= m.BRY; y++ {
		if limit && h.Abs(pos.Y-y) > 15 {
			continue
		}
		for x := m.TLX; x <= m.BRX; x++ {
			chk := h.Coordinate{X: x, Y: y}
			if chk.Equals(pos) {
				fmt.Print("@")
			} else {
				if inPath(chk, path) {
					fmt.Print("O")
				} else {
					fmt.Print(string(m.Get(chk)))
				}
			}
		}
		fmt.Println()
	}
}