too slow for day20

2018/day20/main.go

@@ -0,0 +1,256 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(util.ReadFile("./input.txt"))
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(util.ReadFile("./input.txt"))
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	var furthest int
+
+	coordsToRooms := parseInput(input)
+
+	roomsVisited := make(map[[2]int]bool)
+	queue := [][3]int{{0, 0, 0}} // coord, coord, distance
+	// dijkstra traverse
+	for len(queue) != 0 {
+		front := queue[0]
+		currentCoords := [2]int{front[0], front[1]}
+		currentDistance := front[2]
+		currentRoom := coordsToRooms[[2]int{front[0], front[1]}]
+
+		// do not visit the same room twice
+		if roomsVisited[currentCoords] {
+			queue = queue[1:]
+			continue
+		}
+
+		if furthest < currentDistance {
+			furthest = currentDistance
+		}
+		roomsVisited[currentCoords] = true
+
+		if currentRoom.northDoor {
+			queue = append(queue, [3]int{currentCoords[0] - 1, currentCoords[1], currentDistance + 1})
+		}
+		if currentRoom.southDoor {
+			queue = append(queue, [3]int{currentCoords[0] + 1, currentCoords[1], currentDistance + 1})
+		}
+		if currentRoom.eastDoor {
+			queue = append(queue, [3]int{currentCoords[0], currentCoords[1] + 1, currentDistance + 1})
+		}
+		if currentRoom.westDoor {
+			queue = append(queue, [3]int{currentCoords[0], currentCoords[1] - 1, currentDistance + 1})
+		}
+
+		queue = queue[1:]
+	}
+
+	return furthest
+}
+
+func part2(input string) int {
+	parsed := parseInput(input)
+	_ = parsed
+
+	return 0
+}
+
+type room struct {
+	coords                                   [2]int
+	northDoor, eastDoor, southDoor, westDoor bool
+}
+
+type roomMap map[[2]int]*room
+
+// String method for Stringer interface for easier debugging of a pointer-ed
+// struct so it won't print as just an address
+func (rm roomMap) String() string {
+	ans := "{\n"
+	for _, room := range rm {
+		ans += fmt.Sprintf("coords: %v, NSEW doors: %v %v %v %v\n",
+			room.coords, room.northDoor, room.eastDoor, room.southDoor, room.westDoor)
+	}
+	return ans + "}"
+}
+
+var dirToDiff = map[string][2]int{
+	"N": [2]int{-1, 0},
+	"S": [2]int{1, 0},
+	"E": [2]int{0, 1},
+	"W": [2]int{0, -1},
+}
+
+func parseInput(input string) map[[2]int]*room {
+	coordsToRooms := roomMap{
+		{0, 0}: {coords: [2]int{0, 0}},
+	}
+
+	paths := flattenRegexpPaths(input[1 : len(input)-1])
+
+	// inputRegexp to validate all generated paths - beauty of input being regexp
+	inputRegexp := regexp.MustCompile(input)
+
+	for _, p := range paths {
+		if !inputRegexp.MatchString(p) {
+			panic("BAD PATH: " + p)
+		}
+
+		// step through path and update te coordsToRooms map
+		currentCoords := [2]int{0, 0}
+		for _, dirRune := range p {
+			dir := string(dirRune)
+
+			// if next room is not in map, add it
+			nextRoomCoords := [2]int{
+				currentCoords[0] + dirToDiff[dir][0],
+				currentCoords[1] + dirToDiff[dir][1],
+			}
+			if _, ok := coordsToRooms[nextRoomCoords]; !ok {
+				coordsToRooms[nextRoomCoords] = &room{
+					coords: nextRoomCoords,
+				}
+			}
+
+			switch dir {
+			case "N":
+				coordsToRooms[currentCoords].northDoor = true
+				coordsToRooms[nextRoomCoords].southDoor = true
+			case "S":
+				coordsToRooms[currentCoords].southDoor = true
+				coordsToRooms[nextRoomCoords].northDoor = true
+			case "E":
+				coordsToRooms[currentCoords].eastDoor = true
+				coordsToRooms[nextRoomCoords].westDoor = true
+			case "W":
+				coordsToRooms[currentCoords].westDoor = true
+				coordsToRooms[nextRoomCoords].eastDoor = true
+			default:
+				panic("INVALID DIRECTION" + string(dir))
+			}
+			currentCoords = nextRoomCoords
+		}
+	}
+
+	return coordsToRooms
+}
+
+var noNestedStepsRegexp = regexp.MustCompile("^[NS|EW]*$")
+
+// generates a string of all possible paths, inefficient but easier to parse through
+func flattenRegexpPaths(input string) []string {
+	if noNestedStepsRegexp.MatchString(input) {
+		return strings.Split(input, "|")
+	}
+
+	var paths []string
+	topLevelOptions := breakIntoTopLevelOptions(input)
+
+	for _, step := range topLevelOptions {
+		rootStr, branchStr := ingestNextBalancedParen(step)
+		if rootStr[0] == '(' {
+			rootStr = rootStr[1 : len(rootStr)-1]
+		}
+		rootPaths := flattenRegexpPaths(rootStr)
+		branchPaths := flattenRegexpPaths(branchStr)
+
+		for _, r := range rootPaths {
+			for _, b := range branchPaths {
+				paths = append(paths, r+b)
+			}
+		}
+	}
+
+	return paths
+}
+
+var parensMap = map[string]int{
+	"(": 1,
+	")": -1,
+}
+
+// break into all balanced parens separated by a pipe
+func breakIntoTopLevelOptions(input string) []string {
+	var topLevel []string
+
+	var left, right, parenBalance int
+	for right < len(input) {
+		char := string(input[right])
+		if char == "|" && parenBalance == 0 {
+			topLevel = append(topLevel, input[left:right])
+			right++
+			left = right
+		} else {
+			right++
+			parenBalance += parensMap[char]
+		}
+
+		parenBalance += parensMap[char]
+	}
+
+	if parenBalance != 0 {
+		fmt.Println("top level", topLevel)
+		panic(fmt.Sprintf("paren balance off for %q, %d", input, parenBalance))
+	}
+
+	// append on last option
+	topLevel = append(topLevel, input[left:])
+
+	return topLevel
+}
+
+// splits the string into the first section that's a balanced paren & the rest
+// both sections will be balanced parens
+//
+// if the first character is a paren, it will parse until the string is balanced
+// else it splits at the first paren
+func ingestNextBalancedParen(input string) (balanced string, remainder string) {
+	if len(input) == 0 {
+		return "", ""
+	}
+
+	// if not opening paren, parse up to first open paren
+	if input[0] != '(' {
+		firstParenIndex := strings.Index(input, "(")
+		if firstParenIndex == -1 {
+			return input, ""
+		}
+		return input[:firstParenIndex], input[firstParenIndex:]
+	}
+
+	// otherwise first character is an opening paren
+	index := 1
+	parenBalance := 1
+
+	// assume all in puts are valid - i.e. a panic for out of range input[index]
+	// is a good warning
+	for parenBalance != 0 {
+		char := string(input[index])
+		parenBalance += parensMap[char]
+
+		index++
+	}
+
+	return input[:index], input[index:]
+}