main.go

package main

import (
	"fmt"
	"github.com/danvolchek/AdventOfCode/lib"
)

type node struct {
	x, y int

	adjacent []*node
}

func (n *node) Id() string {
	return fmt.Sprintf("%d,%d", n.y, n.x)
}

func (n *node) Adjacent() []*node {
	return n.adjacent
}

func (n *node) String() string {
	return n.Id()
}

func parse(char byte) int {
	if char == 'S' {
		return 9999999
	}

	if char == 'E' {
		return -2
	}

	return int(char - 'a')
}

func solve(grid [][]int) int {

	var starts []*node
	var end string

	gridMap := make(map[int]map[int]*node)

	for y, line := range grid {
		for x, height := range line {
			n := &node{
				x:        x,
				y:        y,
				adjacent: nil,
			}

			if height == 9999999 {
				starts = append(starts, n)
			}

			if height == -2 {
				end = n.Id()
			}

			if height == 0 {
				starts = append(starts, n)
			}

			if gridMap[y] == nil {
				gridMap[y] = make(map[int]*node)
			}

			gridMap[y][x] = n

			if height == -2 {
				grid[y][x] = parse('z')
			}

			if height == 9999999 {
				grid[y][x] = parse('a')
			}
		}
	}

	for y, line := range grid {
		for x, height := range line {
			for iy := -1; iy <= 1; iy += 1 {
				for ix := -1; ix <= 1; ix += 1 {
					if iy == 0 && ix == 0 {
						continue
					}
					if lib.Abs(iy)+lib.Abs(ix) == 2 {
						continue
					}

					ey := y + iy
					ex := x + ix

					if ey < 0 || ex < 0 || ey >= len(grid) || ex >= len(grid[ey]) {
						continue
					}

					if height >= grid[ey][ex]-1 {
						gridMap[y][x].adjacent = append(gridMap[y][x].adjacent, gridMap[ey][ex])
					}
				}
			}
		}
	}

	distances := lib.Map(starts, func(s *node) (ret int) {
		defer func() {
			if r := recover(); r != nil {
				ret = 9999999999999999
			}
		}()
		result, ok := lib.BFS(s, func(n *node) bool {
			return n.Id() == end
		})
		if !ok {
			panic("not found")
		}

		return len(result) - 1
	})

	return lib.MinSlice(distances)
}

func main() {
	solver := lib.Solver[[][]int, int]{
		ParseF: lib.ParseGrid(parse),
		SolveF: solve,
	}

	solver.Expect("Sabqponm\nabcryxxl\naccszExk\nacctuvwj\nabdefghi", 29)
	solver.Verify(321)
}