advent_of_code_2024/day_10/solution.go

package day_10

import (
	"strings"
)

const Empty = '.'

type Point struct {
	x, y   int
	height rune
}

type TopographicMap [][]rune

func (t TopographicMap) InMap(x, y int) bool {
	return x >= 0 && x < len(t[0]) && y >= 0 && y < len(t)
}

func (t TopographicMap) At(x, y int) rune {
	if t.InMap(x, y) {
		return t[y][x]
	}
	return Empty
}

// task:https://adventofcode.com/2024/day/10
func SolveBasic(input string) int {
	topographicMap := loadMap(input)
	solutions := 0
	for y, line := range topographicMap {
		for x, pos := range line {
			if pos == '0' {
				trails := score(topographicMap, x, y)
				solutions += trails
			}
		}
	}
	return solutions
}

// task:https://adventofcode.com/2024/day/10#part2
func SolveComplex(input string) int {
	topographicMap := loadMap(input)
	solutions := 0
	for y, line := range topographicMap {
		for x, pos := range line {
			if pos == '0' {
				trails := rating(topographicMap, x, y)
				solutions += trails
			}
		}
	}
	return solutions
}

func score(tMap TopographicMap, x int, y int) int {
	queue := []Point{{x, y, '0'}}
	trails := map[Point]bool{}
	for len(queue) > 0 {
		p := queue[0]
		queue = queue[1:]

		if p.height == '9' {
			trails[p] = true
		} else {
			if tMap.At(p.x-1, p.y) == p.height+1 {
				queue = append(queue, Point{p.x - 1, p.y, p.height + 1})
			}
			if tMap.At(p.x, p.y-1) == p.height+1 {
				queue = append(queue, Point{p.x, p.y - 1, p.height + 1})
			}
			if tMap.At(p.x+1, p.y) == p.height+1 {
				queue = append(queue, Point{p.x + 1, p.y, p.height + 1})
			}
			if tMap.At(p.x, p.y+1) == p.height+1 {
				queue = append(queue, Point{p.x, p.y + 1, p.height + 1})
			}
		}
	}
	return len(trails)
}

func rating(tMap TopographicMap, x int, y int) int {
	queue := []Point{{x, y, '0'}}
	trails := 0
	for len(queue) > 0 {
		p := queue[0]
		queue = queue[1:]

		if p.height == '9' {
			trails++
		} else {
			if tMap.At(p.x-1, p.y) == p.height+1 {
				queue = append(queue, Point{p.x - 1, p.y, p.height + 1})
			}
			if tMap.At(p.x, p.y-1) == p.height+1 {
				queue = append(queue, Point{p.x, p.y - 1, p.height + 1})
			}
			if tMap.At(p.x+1, p.y) == p.height+1 {
				queue = append(queue, Point{p.x + 1, p.y, p.height + 1})
			}
			if tMap.At(p.x, p.y+1) == p.height+1 {
				queue = append(queue, Point{p.x, p.y + 1, p.height + 1})
			}
		}
	}
	return trails
}

func loadMap(input string) TopographicMap {
	input = strings.ReplaceAll(input, "\r", "")
	topographicMap := TopographicMap{}
	for _, line := range strings.Split(input, "\n") {
		topographicMap = append(topographicMap, []rune(line))
	}
	return topographicMap
}