adventofcode/2024/day10/main.go

package main

import (
	"fmt"

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

func main() {
	inp := h.StdinToCoordMap()
	part1(inp)
	fmt.Println()
	part2(inp)
}

func part1(inp h.CoordByteMap) {
	var total int
	heads := inp.FindAll('0')
	for _, h := range heads {
		trails := findTrails(inp, h, h, false)
		total = total + len(trails)
	}
	fmt.Println("# Part 1")
	fmt.Println("Scores:", total)
}

func part2(inp h.CoordByteMap) {
	var total int
	heads := inp.FindAll('0')
	for _, h := range heads {
		trails := findTrails(inp, h, h, true)
		total = total + len(trails)
	}
	fmt.Println("# Part 1")
	fmt.Println("Scores:", total)
}

func findTrails(m h.CoordByteMap, st h.Coordinate, curr h.Coordinate, unique bool) []h.Coordinate {
	currBt := m.Get(curr)
	if currBt == '9' {
		return []h.Coordinate{curr}
	}

	var trails []h.Coordinate
	for _, nx := range []h.Coordinate{curr.North(), curr.East(), curr.South(), curr.West()} {
		if m.ContainsCoord(nx) && m.Get(nx) == currBt+1 {
			res := findTrails(m, st, nx, unique)
			if unique {
				trails = append(trails, res...)
			} else {
				trails = appendUnique(trails, res...)
			}
		}
	}
	return trails
}

func appendUnique(sl []h.Coordinate, n ...h.Coordinate) []h.Coordinate {
	if len(n) == 0 {
		return sl
	}
	if len(n) > 1 {
		for j := range n {
			sl = appendUnique(sl, n[j])
		}
		return sl
	}

	for i := range sl {
		if sl[i].Equals(n[0]) {
			return sl
		}
	}
	sl = append(sl, n[0])
	return sl
}