adventofcode/2024/day16/main.go

package main

import (
	"errors"
	"fmt"

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

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

var (
	N = h.Coordinate{X: 0, Y: -1}
	E = h.Coordinate{X: 1, Y: 0}
	S = h.Coordinate{X: 0, Y: 1}
	W = h.Coordinate{X: -1, Y: 0}
)

var (
	scoreTrack    map[h.Coordinate]int
	bestCostToEnd map[h.Coordinate]int
)

func part1(inpS []string) {
	inp := h.StringSliceToCoordByteMap(inpS)
	scoreTrack = make(map[h.Coordinate]int)
	bestCostToEnd = make(map[h.Coordinate]int)

	start, _ := inp.FindFirst('S')
	end, _ := inp.FindFirst('E')
	inp.Put(start, '.')
	bestCostToEnd[end] = 0

	cd := CD{c: start, d: E}
	solve(inp, cd, end, 0, []h.Coordinate{cd.c})
	best, ok := scoreTrack[end]
	if !ok {
		panic(errors.New("no path to end found"))
	}
	fmt.Println("Best Score:", best)

	bestSeats := make(map[h.Coordinate]byte)
	for i := range bestPaths {
		for j := range bestPaths[i] {
			bestSeats[bestPaths[i][j]] = byte('0' + i)
		}
	}
	printBestSeats(inp, bestSeats)
	fmt.Println("Seats:", len(bestSeats))
}

var bestPaths [][]h.Coordinate

func solve(inp h.CoordByteMap, start CD, end h.Coordinate, score int, currPath []h.Coordinate) int {
	// tryMove takes the cd that we're moving to and the cost to move there
	// and returns the cost to get from that cd to the end
	tryMove := func(c CD, cost int) int {
		if inp.ContainsCoord(c.c) && inp.Get(c.c) != '#' {
			// printPathMap(inp, c, end, currPath)
			// poi := h.Coordinate{X: 3, Y: 10}
			// time.Sleep(time.Second / 20)
			nextScore := score + cost
			v, ok := bestCostToEnd[c.c]
			//if c.c.Equals(poi) {
			//	fmt.Println("Current Scoretrack[poi] =", v)
			//	fmt.Println("Next Score =", nextScore)
			//	time.Sleep(time.Second * 5)
			//}
			if !ok || v >= nextScore {
				nxtPath := make([]h.Coordinate, len(currPath))
				copy(nxtPath, currPath)
				nxtPath = append(nxtPath, c.c)

				// Check end conditions
				if c.c.Equals(end) {
					if !ok || v > nextScore { // New Best
						fmt.Println("New Best Path")
						scoreTrack[end] = nextScore
						bestPaths = [][]h.Coordinate{nxtPath}
					} else if v == nextScore { // Another Best Path
						fmt.Println("Adding path to best paths")
						bestPaths = append(bestPaths, nxtPath)
					}
					return cost
				}
				// Not the end, but keep going
				scoreTrack[c.c] = nextScore
				solve(inp, c, end, nextScore, nxtPath)
			}
		}
		return h.MAX_INT
	}
	// Test forward
	cost := tryMove(start.move(), 1)
	// Test CW
	if wrk := tryMove(start.turnCW().move(), 1001); wrk < cost {
		cost = wrk
	}
	// Test CCW
	if wrk := tryMove(start.turnCCW().move(), 1001); wrk < cost {
		cost = wrk
	}
	bestCostToEnd[start.c] = cost
	return cost
}

func printPathMap(inp h.CoordByteMap, loc CD, end h.Coordinate, path []h.Coordinate) {
	fmt.Print(h.CLEAR_SCREEN)
	wrk := inp.Copy()
	wrk.ReplaceAll('.', ' ')
	for i := range path {
		wrk.Put(path[i], 'o')
	}
	wrk.Put(loc.c, loc.Byte())
	fmt.Println(wrk)
	if v, ok := scoreTrack[end]; ok {
		fmt.Printf("Best Score: %v (Paths: %d)\n", v, len(bestPaths))
	} else {
		fmt.Println("Waiting on best score...")
	}
}

func printBestSeats(inp h.CoordByteMap, seats map[h.Coordinate]byte) {
	fmt.Print(h.CLEAR_SCREEN)
	wrk := inp.Copy()
	wrk.ReplaceAll('.', ' ')
	for k, v := range seats {
		wrk.Put(k, byte(0+v))
	}
	fmt.Println(wrk)
}

/*
func part2(inpS []string) {
	inp := h.StringSliceToCoordByteMap(inpS)
	scoreTrack = make(map[h.Coordinate]int)
	start, _ := inp.FindFirst('S')
	end, _ := inp.FindFirst('E')
	inp.Put(start, '.')
	cd := CD{c: start, d: E}
	lookForSeats(inp, cd, end, 0, []h.Coordinate{cd.c})
	_, ok := scoreTrack[end]
	if !ok {
		panic(errors.New("no path to end found"))
	}
	bestSeats := make(map[h.Coordinate]int)
	for i := range bestPaths {
		for j := range bestPaths[i] {
			bestSeats[bestPaths[i][j]] = i
		}
	}
	fmt.Println("Number of Seats:", len(bestSeats))
}



func coordInPath(c h.Coordinate, path []h.Coordinate) bool {
	for i := range path {
		if path[i].Equals(c) {
			return true
		}
	}
	return false
}

func lookForSeats(inp h.CoordByteMap, start CD, end h.Coordinate, score int, path []h.Coordinate) int {
	// Check for finished:
	if start.c.Equals(end) {
		v, ok := scoreTrack[end]
		if !ok || v > score {
			// We have a new best path
			bestPaths = [][]h.Coordinate{path}
			scoreTrack[end] = score
		} else if scoreTrack[end] == score {
			bestPaths = append(bestPaths, path)
		}
		return score
	}

	// Helper func
	canMoveTo := func(p h.Coordinate) bool {
		return inp.ContainsCoord(p) && inp.Get(p) != '#'
	}
	// Keep moving:
	tryMove := func(c CD, cost int) {
		if canMoveTo(c.c) {
			// Check if this path has alread gone through this spot
			nxtPath := make([]h.Coordinate, len(path))
			copy(nxtPath, path)
			if coordInPath(c.c, nxtPath) {
				return
			}
			// Ok, now what's the best score we end up if we make this move?
			nextScore := score + cost
			n, ok := scoreTrack[c.c]
			if !ok || n > nextScore {
				lookForSeats(inp, c, end, nextScore, append(nxtPath, c.c))
			}
		}
	}
	// Test forward
	tryMove(start.move(), 1)
	// Test CW
	tryMove(start.turnCW().move(), 1001)
	// Test CCW
	tryMove(start.turnCCW().move(), 1001)
	return scoreTrack[start.c]
}
*/

type CD struct {
	c h.Coordinate
	d h.Coordinate
}

func (cd CD) move() CD {
	return CD{
		c: cd.c.Add(cd.d),
		d: cd.d,
	}
}

func (cd CD) turnCW() CD {
	var newD h.Coordinate
	switch cd.d {
	case N:
		newD = E
	case E:
		newD = S
	case S:
		newD = W
	case W:
		newD = N
	}
	return CD{
		c: cd.c,
		d: newD,
	}
}

func (cd CD) turnCCW() CD {
	var newD h.Coordinate
	switch cd.d {
	case N:
		newD = W
	case E:
		newD = N
	case S:
		newD = E
	case W:
		newD = S
	}
	return CD{
		c: cd.c,
		d: newD,
	}
}

func (cd CD) Byte() byte {
	switch cd.d {
	case N:
		return '^'
	case E:
		return '>'
	case S:
		return 'v'
	case W:
		return '<'
	}
	return '?'
}