work

2024/go/day21/day21.go

@@ -0,0 +1,181 @@
+package day21
+
+import (
+	"adventofcode2024/utils"
+	"adventofcode2024/utils/dijkstra"
+	"adventofcode2024/utils/memo"
+	"fmt"
+	"math"
+	"strings"
+)
+
+type Pair struct {
+	s dijkstra.Point
+	d dijkstra.Point
+}
+
+type Path struct {
+	path     []dijkstra.Point
+	path_str string
+	cost     int
+}
+
+type State struct {
+	code         string
+	depth        int
+	isNumericPad bool
+}
+
+var numericPad = map[dijkstra.Point]string{
+	{X: 0, Y: 0}: "7", {X: 1, Y: 0}: "8", {X: 2, Y: 0}: "9",
+	{X: 0, Y: 1}: "4", {X: 1, Y: 1}: "5", {X: 2, Y: 1}: "6",
+	{X: 0, Y: 2}: "1", {X: 1, Y: 2}: "2", {X: 2, Y: 2}: "3",
+	{X: 1, Y: 3}: "0", {X: 2, Y: 3}: "A",
+}
+
+var directionPad = map[dijkstra.Point]string{
+	{X: 1, Y: 0}: "^", {X: 2, Y: 0}: "A",
+	{X: 0, Y: 1}: "<", {X: 1, Y: 1}: "v", {X: 2, Y: 1}: ">",
+}
+
+var directions = []dijkstra.Point{{X: 0, Y: 1}, {X: 0, Y: -1}, {X: 1, Y: 0}, {X: -1, Y: 0}}
+
+var lookup_np = get_paths(numericPad)
+var lookup_dp = get_paths(directionPad)
+
+var m *memo.Memo
+
+func init() {
+	m = memo.New(get_shortest_path)
+}
+
+func Part1(input string) int {
+	codes := strings.Split(input, "\n")
+	cost := 0
+	for _, code := range codes {
+		initialState := State{
+			code:         code,
+			depth:        2,
+			isNumericPad: true,
+		}
+		result := m.Get(initialState).(int)
+		cost += result * utils.MustAtoi(code[:len(code)-1])
+	}
+	return cost
+}
+
+func Part2(input string) int {
+	codes := strings.Split(input, "\n")
+	cost := 0
+	for _, code := range codes {
+		initialState := State{
+			code:         code,
+			depth:        25,
+			isNumericPad: true,
+		}
+		result := m.Get(initialState).(int)
+		cost += result * utils.MustAtoi(code[:len(code)-1])
+	}
+	return cost
+}
+
+func get_paths(in map[dijkstra.Point]string) map[Pair][]Path {
+	lookup := make(map[Pair][]Path)
+	data := dijkstra.InputGraph{}
+	for p := range in {
+		for _, dir := range directions {
+			np := dijkstra.Point{X: p.X + dir.X, Y: p.Y + dir.Y}
+			if in[np] != "" {
+				data.Graph = append(data.Graph, dijkstra.InputData{
+					Source:      p,
+					Destination: np,
+					Weight:      1,
+				})
+			}
+		}
+	}
+	graph := dijkstra.CreateGraph(data)
+	for s := range in {
+		for d := range in {
+			paths, cost := dijkstra.GetAllShortestPaths(s, d, graph)
+
+			for _, path := range paths {
+				path_str := ""
+				for x := 1; x < len(path); x++ {
+					f := path[x-1]
+					t := path[x]
+
+					switch {
+					case f.X == t.X && f.Y < t.Y:
+						// Moving verticallY down
+						path_str += "v"
+					case f.X == t.X && f.Y > t.Y:
+						// Moving verticallY up
+						path_str += "^"
+					case f.Y == t.Y && f.X < t.X:
+						// Moving horizontallY right
+						path_str += ">"
+					case f.Y == t.Y && f.X > t.X:
+						// Moving horizontally left
+						path_str += "<"
+					default:
+						// No matching case or invalid input
+						fmt.Println("Invalid direction")
+					}
+
+				}
+				lookup[Pair{s, d}] = append(lookup[Pair{s, d}], Path{path, path_str, cost})
+			}
+
+		}
+	}
+	return lookup
+}
+
+func find_point(in string, lookup map[dijkstra.Point]string) dijkstra.Point {
+	for k, v := range lookup {
+		if v == in {
+			return k
+		}
+	}
+	return dijkstra.Point{}
+}
+
+func get_shortest_path(key interface{}) interface{} {
+	state := key.(State)
+
+	if state.depth < 0 {
+		return len(state.code)
+	}
+
+	// (Optional) If you need to modify the state, work on a copy.
+	newState := state
+	newState.code = "A" + state.code
+
+	cost := 0
+	for x := 0; x<len(newState.code)-1; x++ {
+		pps := shortest_paths(string(newState.code[x]), string(newState.code[x+1]), newState.isNumericPad)
+		min := math.MaxInt // Start with a very high number not just 65535
+		for _, pp := range pps {
+			nextState := State{
+				code:         pp.path_str + "A",
+				depth:        newState.depth - 1,
+				isNumericPad: false,
+			}
+			mm := m.Get(nextState).(int)
+			if mm < min {
+				min = mm
+			}
+		}
+		cost += min
+	}
+	return cost
+}
+
+func shortest_paths(s, d string, isNumericPad bool) []Path {
+	if isNumericPad {
+		return lookup_np[Pair{s: find_point(s, numericPad), d: find_point(d, numericPad)}]
+	} else {
+		return lookup_dp[Pair{s: find_point(s, directionPad), d: find_point(d, directionPad)}]
+	}
+}