From 06dada9c63822457ba1cff0f9da44f59fef59647 Mon Sep 17 00:00:00 2001
From: Brian Buller <brian@bullercodeworks.com>
Date: Sat, 21 Dec 2024 08:54:14 -0600
Subject: [PATCH] 2024 Day 21 Complete

---
 2024/day21/input     |   5 ++
 2024/day21/main.go   | 162 +++++++++++++++++++++++++++++++++++++++++++
 2024/day21/testinput |   5 ++
 3 files changed, 172 insertions(+)
 create mode 100644 2024/day21/input
 create mode 100644 2024/day21/main.go
 create mode 100644 2024/day21/testinput

diff --git a/2024/day21/input b/2024/day21/input
new file mode 100644
index 0000000..280ea40
--- /dev/null
+++ b/2024/day21/input
@@ -0,0 +1,5 @@
+836A
+540A
+965A
+480A
+789A
diff --git a/2024/day21/main.go b/2024/day21/main.go
new file mode 100644
index 0000000..3552995
--- /dev/null
+++ b/2024/day21/main.go
@@ -0,0 +1,162 @@
+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
+}
diff --git a/2024/day21/testinput b/2024/day21/testinput
new file mode 100644
index 0000000..4cf0c29
--- /dev/null
+++ b/2024/day21/testinput
@@ -0,0 +1,5 @@
+029A
+980A
+179A
+456A
+379A