Day9 Solution

day9/day9.go

@@ -0,0 +1,118 @@
+package day9
+
+import (
+	"log"
+	"math"
+	"strconv"
+	"strings"
+)
+
+func Day9Logic() (int, int) {
+	return day9Part1(), day9Part2()
+}
+
+var visitedTPart1 = map[[2]int]bool{}
+var visitedTPart2 = map[[2]int]bool{}
+
+func calcGap(head, tail [2]int) float64 {
+	return math.Sqrt(math.Pow(math.Abs(float64(head[0]-tail[0])), 2) + math.Pow(math.Abs(float64(head[1]-tail[1])), 2))
+}
+
+func day9Part1() int {
+	input := strings.Split(input9, "\n")
+	knots := [2][2]int{{0, 0}, {0, 0}}
+	head := knots[0]
+	tail := knots[1]
+	visitedTPart1[tail] = true
+	for _, hMove := range input {
+		dirAndSteps := strings.Split(hMove, " ")
+		dir := dirAndSteps[0]
+		steps, _ := strconv.Atoi(dirAndSteps[1])
+		for i := 0; i < steps; i++ {
+			switch dir {
+			case "U":
+				{
+					head[1]++
+					gap := calcGap(head, tail)
+					if gap > math.Sqrt(2) {
+						tail = [2]int{head[0], head[1] - 1}
+					}
+					visitedTPart1[tail] = true
+				}
+			case "R":
+				{
+					head[0]++
+					gap := calcGap(head, tail)
+					if gap > math.Sqrt(2) {
+						tail = [2]int{head[0] - 1, head[1]}
+					}
+					visitedTPart1[tail] = true
+				}
+			case "D":
+				{
+					head[1]--
+					gap := calcGap(head, tail)
+					if gap > math.Sqrt(2) {
+						tail = [2]int{head[0], head[1] + 1}
+					}
+					visitedTPart1[tail] = true
+				}
+			case "L":
+				{
+					head[0]--
+					gap := calcGap(head, tail)
+					if gap > math.Sqrt(2) {
+						tail = [2]int{head[0] + 1, head[1]}
+					}
+					visitedTPart1[tail] = true
+				}
+			}
+		}
+	}
+	return len(visitedTPart1)
+}
+
+func day9Part2() int {
+
+	input := strings.Split(input9, "\n")
+	knots := [10][2]int{{0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}}
+	visitedTPart2[knots[8]] = true
+	for _, hMove := range input {
+		dirAndSteps := strings.Split(hMove, " ")
+		dir := dirAndSteps[0]
+		steps, _ := strconv.Atoi(dirAndSteps[1])
+		log.Printf("move: %v", hMove)
+		for i := 0; i < steps; i++ {
+			switch dir {
+			case "U":
+				knots[0][1]++
+			case "R":
+				knots[0][0]++
+			case "D":
+				knots[0][1]--
+			case "L":
+				knots[0][0]--
+			}
+			for k := 1; k < 10; k++ {
+				gap := calcGap(knots[k], knots[k-1])
+				gapX := knots[k-1][0] - knots[k][0]
+				gapY := knots[k-1][1] - knots[k][1]
+				if gap > math.Sqrt(2) {
+					knots[k] = [2]int{knots[k][0] + shiftDir(gapX), knots[k][1] + shiftDir(gapY)}
+				}
+			}
+			visitedTPart2[knots[9]] = true
+		}
+	}
+	return len(visitedTPart2)
+}
+
+func shiftDir(diff int) int {
+	if diff > 0 {
+		return 1
+	}
+	if diff == 0 {
+		return 0
+	}
+	return -1
+}