130 lines
2.4 KiB
Go
130 lines
2.4 KiB
Go
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package main
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import (
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"fmt"
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"log"
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"math"
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"os"
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"strconv"
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)
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func main() {
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if len(os.Args) < 2 {
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fmt.Println("Usage: day03 <target>")
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os.Exit(0)
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}
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target := Atoi(os.Args[1])
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fmt.Println("== Part 1 ==")
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part1(target)
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fmt.Println("== Part 2 ==")
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part2(target)
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}
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func part1(target int) {
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idx := 1
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lyrSz := 1
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sizeSquare := int(math.Pow(float64(lyrSz), 2))
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for sizeSquare < target {
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lyrSz += 2
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idx += 1
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sizeSquare = int(math.Pow(float64(lyrSz), 2))
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}
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diff := sizeSquare - target
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lyrJmp := lyrSz - 1
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// Find the side it's on
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side := int(diff / lyrJmp)
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perps := make([]int, 4)
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perps[0] = sizeSquare - (lyrJmp / 2)
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perps[1] = perps[0] - lyrJmp
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perps[2] = perps[1] - lyrJmp
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perps[3] = perps[2] - lyrJmp
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fmt.Println("Distance: ", int(math.Abs(float64(perps[side]-target)))+(idx-1))
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}
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const (
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DIR_E = iota
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DIR_N
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DIR_W
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DIR_S
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DIR_ERROR
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)
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var memMap map[string]int
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var lastX, lastY int
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var lastDir int
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func part2(target int) {
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lastDir = DIR_S
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lastX, lastY = 0, 0
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val := 1
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memMap = make(map[string]int)
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memMap[getMapKey(lastX, lastY)] = val
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for val <= target {
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// Find the coordinate for the next one
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lastX, lastY, lastDir = findNextMapPos()
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val = getAdjacentSum(lastX, lastY)
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memMap[getMapKey(lastX, lastY)] = val
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}
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fmt.Println("Result:", val, "at", getMapKey(lastX, lastY))
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}
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func getAdjacentSum(posX, posY int) int {
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res := 0
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for _, x := range []int{-1, 0, 1} {
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for _, y := range []int{-1, 0, 1} {
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if x == 0 && y == 0 {
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continue
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}
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if i, ok := memMap[getMapKey((posX+x), (posY+y))]; ok {
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res += i
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}
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}
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}
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return res
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}
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func findNextMapPos() (int, int, int) {
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// First check if the current pos is empty
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if _, ok := memMap[getMapKey(lastX, lastY)]; !ok {
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return lastX, lastY, lastDir
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}
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// Check if the wrapping direction is free
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nextDir := (lastDir + 1) % DIR_ERROR
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testX, testY := getXYInDir(nextDir)
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if _, ok := memMap[getMapKey(testX, testY)]; ok {
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testX, testY = getXYInDir(lastDir)
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nextDir = lastDir
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}
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// Otherwise continue in lastDir
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return testX, testY, nextDir
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}
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func getXYInDir(dir int) (int, int) {
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testX, testY := lastX, lastY
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switch dir {
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case DIR_E:
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testX++
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case DIR_N:
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testY--
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case DIR_W:
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testX--
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case DIR_S:
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testY++
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}
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return testX, testY
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}
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func getMapKey(xPos, yPos int) string {
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return fmt.Sprintf("%d;%d", xPos, yPos)
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}
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func Atoi(i string) int {
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var ret int
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var err error
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if ret, err = strconv.Atoi(i); err != nil {
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log.Fatal("Invalid Atoi")
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}
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return ret
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}
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