Rename day 03 "main.go" -> "day03.go"

2017/day03/day03.go

@@ -0,0 +1,129 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"strconv"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage:	day03 <target>")
+		os.Exit(0)
+	}
+	target := Atoi(os.Args[1])
+	fmt.Println("== Part 1 ==")
+	part1(target)
+	fmt.Println("== Part 2 ==")
+	part2(target)
+}
+
+func part1(target int) {
+	idx := 1
+	lyrSz := 1
+	sizeSquare := int(math.Pow(float64(lyrSz), 2))
+	for sizeSquare < target {
+		lyrSz += 2
+		idx += 1
+		sizeSquare = int(math.Pow(float64(lyrSz), 2))
+	}
+	diff := sizeSquare - target
+	lyrJmp := lyrSz - 1
+	// Find the side it's on
+	side := int(diff / lyrJmp)
+	perps := make([]int, 4)
+	perps[0] = sizeSquare - (lyrJmp / 2)
+	perps[1] = perps[0] - lyrJmp
+	perps[2] = perps[1] - lyrJmp
+	perps[3] = perps[2] - lyrJmp
+	fmt.Println("Distance: ", int(math.Abs(float64(perps[side]-target)))+(idx-1))
+}
+
+const (
+	DIR_E = iota
+	DIR_N
+	DIR_W
+	DIR_S
+	DIR_ERROR
+)
+
+var memMap map[string]int
+var lastX, lastY int
+var lastDir int
+
+func part2(target int) {
+	lastDir = DIR_S
+	lastX, lastY = 0, 0
+
+	val := 1
+	memMap = make(map[string]int)
+	memMap[getMapKey(lastX, lastY)] = val
+	for val <= target {
+		// Find the coordinate for the next one
+		lastX, lastY, lastDir = findNextMapPos()
+		val = getAdjacentSum(lastX, lastY)
+		memMap[getMapKey(lastX, lastY)] = val
+	}
+	fmt.Println("Result:", val, "at", getMapKey(lastX, lastY))
+}
+
+func getAdjacentSum(posX, posY int) int {
+	res := 0
+	for _, x := range []int{-1, 0, 1} {
+		for _, y := range []int{-1, 0, 1} {
+			if x == 0 && y == 0 {
+				continue
+			}
+			if i, ok := memMap[getMapKey((posX+x), (posY+y))]; ok {
+				res += i
+			}
+		}
+	}
+	return res
+}
+
+func findNextMapPos() (int, int, int) {
+	// First check if the current pos is empty
+	if _, ok := memMap[getMapKey(lastX, lastY)]; !ok {
+		return lastX, lastY, lastDir
+	}
+	// Check if the wrapping direction is free
+	nextDir := (lastDir + 1) % DIR_ERROR
+	testX, testY := getXYInDir(nextDir)
+	if _, ok := memMap[getMapKey(testX, testY)]; ok {
+		testX, testY = getXYInDir(lastDir)
+		nextDir = lastDir
+	}
+	// Otherwise continue in lastDir
+	return testX, testY, nextDir
+}
+
+func getXYInDir(dir int) (int, int) {
+	testX, testY := lastX, lastY
+	switch dir {
+	case DIR_E:
+		testX++
+	case DIR_N:
+		testY--
+	case DIR_W:
+		testX--
+	case DIR_S:
+		testY++
+	}
+	return testX, testY
+}
+
+func getMapKey(xPos, yPos int) string {
+	return fmt.Sprintf("%d;%d", xPos, yPos)
+}
+
+func Atoi(i string) int {
+	var ret int
+	var err error
+	if ret, err = strconv.Atoi(i); err != nil {
+		log.Fatal("Invalid Atoi")
+	}
+	return ret
+}