AOC2022/day12/day12.go

package main

import (
	"AOC2022/helper"
	"fmt"
	"os"
)

type FieldPoint struct {
	cost   int
	height int
	before [2]int
}

func main() {
	args := os.Args[1:]
	lines := helper.ReadTextFile(args[0])
	start, end := getStartingPointAndEndpoint(lines)
	fmt.Println(start)
	fmt.Println(end)
	field := getField(lines)
	part1(field, start, end)
	part2(lines, field, end)

}

func part2(lines []string, field [][]FieldPoint, end [2]int) {
	lowestPoints := getLowestPoints(lines)
	fastestPath := 999999
	for _, point := range lowestPoints {
		activePoints := make(map[[2]int]struct{})
		activePoints[[2]int{point[0], point[1]}] = struct{}{}
		field = getField(lines)
		steps := getBestRouteLength(activePoints, field, end)
		if steps < fastestPath && steps != 0 {
			fastestPath = steps
		}
	}
	fmt.Println(fastestPath)
}

func part1(field [][]FieldPoint, start, end [2]int) {
	activePoints := make(map[[2]int]struct{})
	activePoints[start] = struct{}{}
	fmt.Println(getBestRouteLength(activePoints, field, end))
}

func getField(lines []string) [][]FieldPoint {
	field := make([][]FieldPoint, len(lines))
	for i := 0; i < len(lines); i++ {
		line := lines[i]
		fieldLine := make([]FieldPoint, len(line))
		for j := 0; j < len(line); j++ {
			height := int(line[j])
			if line[j] == 'S' {
				height = int('a')
			}
			if line[j] == 'E' {
				height = int('z')
			}
			fieldLine[j] = FieldPoint{0, height, [2]int{-1, -1}}
		}
		field[i] = fieldLine
	}
	return field
}

func getBestRouteLength(activePoints map[[2]int]struct{}, field [][]FieldPoint, endPoint [2]int) int {
	for len(activePoints) > 0 {
		step(&field, &activePoints)
	}
	return field[endPoint[0]][endPoint[1]].cost
}

func step(field *[][]FieldPoint, activePoints *map[[2]int]struct{}) {
	point := get_some_key(*activePoints)
	delete(*activePoints, point)
	current0 := point[0]
	current1 := point[1]
	currentFieldSumCost := (*field)[current0][current1].cost
	directions := [4][2]int{{0, -1}, {+1, 0}, {0, 1}, {-1, 0}}
	for _, direction := range directions {
		toVisit0 := current0 + direction[0]
		toVisit1 := current1 + direction[1]
		if checkVisitable(point, direction, *field) {
			cost := 1 + currentFieldSumCost
			if (*field)[toVisit0][toVisit1].cost > cost || (*field)[toVisit0][toVisit1].cost == 0 {
				(*field)[toVisit0][toVisit1].cost = cost
				(*field)[toVisit0][toVisit1].before = [2]int{current0, current1}
				(*activePoints)[[2]int{toVisit0, toVisit1}] = struct{}{}
			}
		}
	}
}

func checkVisitable(activePosition [2]int, direction [2]int, field [][]FieldPoint) (visitable bool) {
	toVisit := activePosition
	toVisit[0] += direction[0]
	toVisit[1] += direction[1]
	if toVisit[0] > -1 && toVisit[1] > -1 &&
		toVisit[0] < len(field) && toVisit[1] < len((field)[0]) &&
		field[activePosition[0]][activePosition[1]].before != toVisit {
		heightToVisit := field[toVisit[0]][toVisit[1]].height
		heightCurrentPos := field[activePosition[0]][activePosition[1]].height + 1
		if heightToVisit > heightCurrentPos {
			return false
		}
		return true
	}
	return false
}

func getStartingPointAndEndpoint(field []string) (start, end [2]int) {
	for i := 0; i < len(field); i++ {
		for j := 0; j < len(field[i]); j++ {
			if field[i][j] == 'S' {
				start = [2]int{i, j}
			}
			if field[i][j] == 'E' {
				end = [2]int{i, j}
			}
		}
	}
	return
}

func getLowestPoints(field []string) [][2]int {
	lowestPoints := [][2]int{}
	for i := 0; i < len(field); i++ {
		for j := 0; j < len(field[i]); j++ {
			if field[i][j] == 'a' {
				lowestPoints = append(lowestPoints, [2]int{i, j})
			}
		}
	}
	return lowestPoints
}

func get_some_key(m map[[2]int]struct{}) [2]int {
	for k := range m {
		return k
	}
	return [2]int{-1, -1}
}

func print(field [][]FieldPoint) {
	for i := 0; i < len(field); i++ {
		fieldLine := field[i]
		tempArray := []int{}
		for j := 0; j < len(fieldLine); j++ {
			tempArray = append(tempArray, fieldLine[j].height-96)
		}
		fmt.Println(tempArray)
	}
	fmt.Println()
	for i := 0; i < len(field); i++ {
		fieldLine := field[i]
		tempArray := []int{}
		for j := 0; j < len(fieldLine); j++ {
			tempArray = append(tempArray, fieldLine[j].cost)
		}
		fmt.Println(tempArray)
	}
}