adventofcode/2024/day21/main.go

package main

import (
	"fmt"
	"strings"

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

func main() {
	inp := h.StdinToStringSlice()
	dirPad := make(map[string]h.Coordinate)
	dirPad["A"] = h.Coordinate{X: 2, Y: 1}
	dirPad["^"] = h.Coordinate{X: 1, Y: 1}
	dirPad[">"] = h.Coordinate{X: 2, Y: 0}
	dirPad["v"] = h.Coordinate{X: 1, Y: 0}
	dirPad["<"] = h.Coordinate{X: 0, Y: 0}

	numPad := make(map[string]h.Coordinate)
	numPad["A"] = h.Coordinate{X: 2, Y: 0}
	numPad["0"] = h.Coordinate{X: 1, Y: 0}
	numPad["1"] = h.Coordinate{X: 0, Y: 1}
	numPad["2"] = h.Coordinate{X: 1, Y: 1}
	numPad["3"] = h.Coordinate{X: 2, Y: 1}
	numPad["4"] = h.Coordinate{X: 0, Y: 2}
	numPad["5"] = h.Coordinate{X: 1, Y: 2}
	numPad["6"] = h.Coordinate{X: 2, Y: 2}
	numPad["7"] = h.Coordinate{X: 0, Y: 3}
	numPad["8"] = h.Coordinate{X: 1, Y: 3}
	numPad["9"] = h.Coordinate{X: 2, Y: 3}
	fmt.Println("# Part 1")
	fmt.Println(findOrders(inp, dirPad, numPad, 2))
	fmt.Println("")
	fmt.Println("# Part 2")
	fmt.Println(findOrders(inp, dirPad, numPad, 25))
}

func parseNum(line string) int {
	var numLine string
	for i := range line {
		if line[i] >= '0' && line[i] <= '9' {
			numLine = numLine + string(line[i])
		}
	}
	var num int
	fmt.Sscanf(numLine, "%d", &num)
	return num
}

// findOrders takes:
//
//		inp: The codes that need to be input
//	 dirPad: The direction pad description
//	 numPad: The number pad description
//	 bots: How many robots are operating directional pads between you and the numpad robot.
func findOrders(inp []string, dirPad, numPad map[string]h.Coordinate, bots int) int {
	var count int
	cache := make(map[string][]int)
	for _, line := range inp {
		code := strings.Split(line, "")
		s := workPad(code, "A", numPad)
		wrk := workBots(s, bots, 1, cache, dirPad)
		count += parseNum(line) * wrk
	}
	return count
}

func workPad(code []string, start string, pad map[string]h.Coordinate) []string {
	curr := pad[start]
	out := []string{}
	for _, c := range code {
		btn := pad[c]
		dist := btn.Sub(curr)
		var outV, outH []string
		for i := 0; i < h.Abs(dist.X); i++ {
			if dist.X >= 0 {
				outH = append(outH, ">")
			} else {
				outH = append(outH, "<")
			}
		}
		for i := 0; i < h.Abs(dist.Y); i++ {
			if dist.Y >= 0 {
				outV = append(outV, "^")
			} else {
				outV = append(outV, "v")
			}
		}
		_, isNumPad := pad["0"]
		if isNumPad {
			if curr.Y == 0 && btn.X == 0 {
				out = append(out, outV...)
				out = append(out, outH...)
			} else if (curr.X == 0 && btn.Y == 0) || dist.X < 0 {
				out = append(out, outH...)
				out = append(out, outV...)
			} else if dist.X >= 0 {
				out = append(out, outV...)
				out = append(out, outH...)
			}
		} else {
			if curr.X == 0 && btn.Y == 1 {
				out = append(out, outH...)
				out = append(out, outV...)
			} else if curr.Y == 1 && btn.X == 0 {
				out = append(out, outV...)
				out = append(out, outH...)
			} else if dist.X < 0 {
				out = append(out, outH...)
				out = append(out, outV...)
			} else if dist.X >= 0 {
				out = append(out, outV...)
				out = append(out, outH...)
			}
		}
		curr = btn
		out = append(out, "A")
	}
	return out
}

func workBots(inst []string, bots int, bot int, cache map[string][]int, dirPad map[string]h.Coordinate) int {
	cacheKey := strings.Join(inst, "")
	if v, ok := cache[cacheKey]; ok {
		if v[bot-1] != 0 {
			return v[bot-1]
		}
	} else {
		cache[cacheKey] = make([]int, bots)
	}
	s := workPad(inst, "A", dirPad)
	cache[cacheKey][0] = len(s)
	if bot == bots {
		return len(s)
	}
	sSteps := splitSteps(s)
	var count int
	for _, s := range sSteps {
		c := workBots(s, bots, bot+1, cache, dirPad)
		subCacheKey := strings.Join(s, "")
		if _, ok := cache[subCacheKey]; !ok {
			cache[subCacheKey] = make([]int, bots)
		}
		cache[subCacheKey][0] = c
		count += c
	}
	cache[cacheKey][bot-1] = count
	return count
}

func splitSteps(s []string) [][]string {
	var out [][]string
	var c []string
	for _, char := range s {
		c = append(c, char)
		if char == "A" {
			out = append(out, c)
			c = []string{}
		}
	}
	return out
}